Article pubs.acs.org/IC
Ruthenium Derivatives of in Situ Generated Redox-Active 1,2Dinitrosobenzene and 2‑Nitrosoanilido. Diverse Structural and Electronic Forms Prabir Ghosh, Soumyodip Banerjee, and Goutam Kumar Lahiri* Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India S Supporting Information *
ABSTRACT: The article describes one-pot synthesis and structural elucidation of tc-[RuII(pap)2(L•−)]ClO4 [1]ClO4 and tc-[RuII(pap)2(L′−)]ClO4 [2]ClO4, which were obtained from tc-[RuII(pap)2(EtOH)2](ClO4)2 and benzofuroxan (L = 1,2-dinitrosobenzene, an intermediate tautomeric form of the biologically active benzofuroxan, L′− = 2-nitrosoanilido, pap = 2phenylazopyridine, tc = trans and cis corresponding to pyridine and azo nitrogen donors of pap, respectively). The same reaction with the newly synthesized and structurally characterized metal precursor cc-RuII(2,6-dichloropap)2Cl2, however, affords isomeric ct-[RuII(2,6-dichloropap)2(L•−)]+ (3a+) and tc[RuII(2,6-dichloropap)2(L•−)]+ (3b+) (cc, ct, and tc with respect to pyridine and azo nitrogens of 2,6-dichloropap) with the structural authentication of elusive ct-isomeric form of {Ru(pap)2} family. The impact of trans or cis orientation of the nitroso group of L/L′ with respect to the NN (azo) function of pap in the complexes was reflected in the relative lengthening or shortening of the latter distance, respectively. The redoxsensitive bond parameters of 1+ and 3+ reveal the intermediate radical form of L•−, while 2+ involves in situ generated L′−. The multiple redox processes of the complexes in CH3CN are analyzed via experimental and density functional theory (DFT) and time-dependent DFT calculations. One-electron oxidation of the electron paramagnetic resonance-active radical species (1+ and 3+) leads to [RuII(pap)2(L)]2+ involving fully oxidized L0 in 12+ and 32+; the same in 2+ results in a radical species [RuII(pap)2(L′•)]2+ (22+). Successive reductions in each case are either associated with pap or L/L′−-based orbitals, revealing a competitive scenario relating to their π-accepting features. The isolated or electrochemically generated radical species either by oxidation or reduction exhibits near-IR transitions in each case, attributing diverse electronic structures of the complexes in accessible redox states.
■
INTRODUCTION The present article originates from our ongoing research interest in exploring the delicate electronic structural aspects of newer molecular frameworks involving redox-facile metal ion and ligand.1 The participation of such ligand moieties along the redox chain of the complexes modulates the electrophilicity or nucleophilicity of the metal ion, which in effect facilitates important organic transformations that are otherwise considered to be difficult by following the standard synthetic routes.2 In this context, transition-metal complexes of conventional redox-active ligands such as quinones,3 iminoquinones,4 diimines,5 dithiolene,6 azoaromatics,7 nitrosyl,8 and porphyrins9 are subjected to continuous scrutiny primarily due to their intrinsic valence/spin configurations at the metal−ligand interface. However, noninnocent feature of nindigo,10 indigo,11 formazanate,12 β-dikitiminate,13 and nitrosobenzene14 has recently been ascertained in selective coordination environment. The proximity of the frontier orbitals of such ligands and metal ion often leads to an intermediate resonating description instead of any precise situation.15 © XXXX American Chemical Society
The new member of the redox-active ligand family, that is, 1,2-dinitrosoarene (L), an intermediate tautomeric form of the biologically active benzofuroxan16 (Chart 1), has recently been introduced in combination with selective metal fragment {Ru(bpy)2} or {Ru([9]aneS3)} (bpy = 2,2′-bipyridine, [9]aneS3 = 1,4,7-trithiacyclononane; Chart 2) with the structural characterization of its both neutral (L0) and radical (L•−) forms.17 Chart 1. Tautomeric Forms of Benzofuroxan
Received: September 13, 2016
A
DOI: 10.1021/acs.inorgchem.6b02197 Inorg. Chem. XXXX, XXX, XXX−XXX
Article
Inorganic Chemistry
pap)2Cl2 metal precursor (ccc = cis orientations of chlorides and pyridine, azo nitrogens of 2,6-dichloropap, respectively), has failed to yield the corresponding 2-nitrosoanilido (L′) derivative. The said reaction, however, results in L•− radical derived isomeric ct-3a+ and tc-3b+ (ct: cis and trans and tc: trans and cis configurations of pyridine and azo nitrogen donors of 2,6-dichloropap, respectively, Scheme 1). The present article addresses the following aspects: (i) Synthesis, spectroscopic, electrochemical, and structural characterization of all the cationic complexes [1]ClO4, [2]ClO4, [3a]ClO4, [3b]ClO4 in addition to the newly designed metal precursors ccc-Ru(2,6-dichloropap)2Cl2 and tcc-Ru(2,6-dichloropap)2Cl2. (ii) Diverse electronic structural features of 1n/3n and 2n along the accessible redox states. (iii) The effect of selective introduction of 2,6-dichloropap toward the product distribution pattern as well as an unusual isomerization process including the structural evidence of the elusive ct-isomeric form of {Ru(pap)2} family19 in [3a]ClO4. (iv) A comparative account between 1n and previously reported analogous system [Ru(bpy)2(L)]n (4n).17
Chart 2. Redox Series of Dinitrosoarene
Since electronic structure of a particular redox-active ligand framework is known to be sensitive to the nature of the metal fragment,18 we therefore intended to evaluate the impact of {Ru(pap)2} encompassing strongly π-accepting 2-phenylazopyridine (pap) toward the valence and spin distributions at the Ru-1,2-dinitrosobenzene (L) interface. To our delight, in contrast to the reported {Ru(bpy)2} or {Ru([9]aneS3)}, the interaction of tc-{Ru(pap)2} metal fragment (tc = trans and cis orientations of pyridine and azo nitrogens of pap, respectively) with benzofuroxan generates the hitherto unexplored redox-active 2-nitrosoanilido derived tc[Ru(pap)2(L′−)]+ (2+) along with the stable radical species tc[Ru(pap)2(L•−)]+ (1+; Scheme 1) with the retention of tc configuration of the metal precursor.
■
RESULTS AND DISCUSSION Synthesis, General Characterization, and Isomerization. The reaction of benzofuroxan with the metal precursor tc[Ru(pap)2(EtOH)2]2+ (pap = 2-phenylazopyridine, tc = trans and cis orientations of pyridine and azo nitrogens of pap, respectively) in refluxing ethanol under dinitrogen atmosphere followed by chromatographic purification on a neutral alumina column results in tc-[Ru(pap)2(L)]ClO4 ([1]ClO4) and tc[Ru(pap)2(L′)]ClO4 ([2]ClO4) in 3:1 ratio. Structural analysis and other studies (see later) reveal that {Ru(pap)2} unit is linked to the radical anionic state of 1,2-dinitrosobenzene (L; Chart 2) in 1+ as in analogous [Ru(bpy)2(L•−)]+ (4+),17 while 2+ represents [Ru(pap)2(L′−)]+ encompassing 2-nitrosoanilido (L′−) moiety (Scheme 1, Experimental Section). The tc configuration of precursor {Ru(pap)2} fragment was retained in both 1+ and 2+ as in numerous complexes derived from the same metal fragment.20 The strong π-acceptor feature of pap might have played a key role in facilitating the reduction of one of the NO groups of L in 1+ to L′− in 2+ in the presence of protonated solvent. Note that only two reports of metalcoordinated L′− with Ni(II), Cu(II), Pd(II), Hg(II), Fe(II),21 and Ru(II) ([TpRuCl{N(O)C5H3-tBu-NH-κ2-N,N}, Tp = hydridotris(pyrazolyl)borate)])22 are available, but its redox feature has not been addressed so far. Under aforesaid reaction condition, the use of newly developed and structurally characterized 2,6-dichloro substituted pap-derived metal precursor cc-Ru(2,6-dichloropap)2Cl2
Scheme 1. Representation of Complexes
However, selective introduction of Cl groups at the 2,6positions of the pendant phenyl ring of pap (i.e., 2,6dichloropap) in the newly developed ccc-Ru(2,6-dichloroScheme 2. Isomeric Forms of {Ru(pap)2(X)2}
B
DOI: 10.1021/acs.inorgchem.6b02197 Inorg. Chem. XXXX, XXX, XXX−XXX
Article
Inorganic Chemistry (cc represents cis configuration of both pyridine and azo nitrogens of 2,6-dichloropap) yielded isomeric [Ru(2,6dichloropap)2(L•−)]+, ct-3a+ and tc-3b+ (ct (cis, trans) and tc (trans, cis) orientations of pyridine and azo nitrogens of 2,6dichloropap, respectively) involving radical anionic state of L in 4:1 ratio along with negligible (detectable only by mass spectrometry of the reaction mixture) amount of 2-nitrosoanilido (L′−) complex [Ru(2,6-dichloropap)2(L′−)]+. The isomeric ct-3a+ and tc-3b+ are perfectly stable even under refluxing (CH3CN) condition. Unlike tc-{Ru(pap)2} in 1+, the cc configuration of the precursor {Ru(2,6-dichloropap)2} is transformed to ct and tc forms in isomeric 3a+ and 3b+. The formation of ct form in 3a+ can be attributed to a lesser steric constraint between the two bulkier aryl groups of 2,6-dichloropap. The tc form in 3b+ is considered to be driven by its greater thermodynamic stability.23 {Ru(pap)2}-derived octahedral species incorporating monodentate or chelated X,X donors can in principle exhibit five (ctc, ccc, cct, ttt, tcc) or three (ctc, ccc, cct) isomeric (geometrical) forms based on relative orientations of X, pyridine, and azo nitrogens of pap, respectively (Scheme 2). The isomeric forms ctc, ccc, ttt, and tcc have already been structurally characterized under different coordination situations; cct isomer is however defined as a theromodynamically unstable form.19,24 The complex 3a+ is therefore representing the first example of structurally characterized ct-isomeric form of {Ru(pap)2} family. 1:1 conducting [1]ClO4, [2]ClO4, [3a]ClO4, [3b]ClO4 complexes were characterized by standard analytical techniques (mass (Figure S1 in the Supporting Information), IR, and microanalysis; see Experimental Section). The 1H NMR spectra of paramagnetic 1+, 3a+, and 3b+ display broad proton resonances, while diamagnetic 2+ exhibits calculated number of sharp aromatic proton signals in addition to D2O exchangeable NH proton of L′ (Figure S2 in the Supporting Information and Experimental Section). Molecular Structures. Molecular geometries including isomeric identities of [1]ClO4, [2]ClO4, [3a]ClO4, [3b]ClO4, and newly designed metal precursors (ccc-Ru(2,6-dichloropap)2Cl2 and tcc-Ru(2,6-dichloropap)2Cl2) were authenticated by their single-crystal X-ray structures (Figures 1−4 and Table 1; see also Figure S3 and Tables S1−S6 in the Supporting Information). This reveals nitrogen donors of NO,NO and
Figure 2. Perspective view of the cationic part of [2]ClO4. Ellipsoids are drawn at 30% probability level. Hydrogen atoms and solvent molecule are omitted for clarity.
Figure 3. Perspective view of the cationic part of [3a]ClO4. Ellipsoids are drawn at 30% probability level. Hydrogen atoms are omitted for clarity.
Figure 4. Perspective view of the cationic part of [3b]ClO4. Ellipsoids are drawn at 50% probability level. Hydrogen atoms and solvent molecules are omitted for clarity.
NO,NH of L and L′ in [1]ClO4, [3a]ClO4, [3b]ClO4, and [2]ClO4, respectively, are coordinated to {Ru(pap)2} or {Ru(2,6-dichloropap)2}, forming five-membered chelate in each case with N−Ru−N bite angle of 78.8(3)°−80.3(2)°. The average trans angles in [1]ClO4, [2]ClO4, [3a]ClO4, and
Figure 1. Perspective view of the cationic part of [1]ClO4. Ellipsoids are drawn at 50% probability level. Hydrogen atoms and solvent molecules are omitted for clarity. C
DOI: 10.1021/acs.inorgchem.6b02197 Inorg. Chem. XXXX, XXX, XXX−XXX
Article
Inorganic Chemistry
Table 1. Experimental and DFT-Calculated Selected Bond Lengths (Å) for [1]ClO4·C6H6·C3H3, [2]ClO4·C6H6, [3a]ClO4, and [3b]ClO4·C6H6·H2O [1]ClO4·C6H6·C3H3
[2]ClO4·C6H6
[3b]ClO4·C6H6·H2O
[3a]ClO4
bond length (Å)
X-ray
DFT
X-ray
DFT
X-ray
DFT
X-ray
DFT
Ru1−N1 Ru1−N2 Ru1−N3 Ru1−N4 Ru1−N5 Ru1−N6 Ru1−N8 N1−O1 N2−O2 C1−C6 C1−C#1 C1−N1 C6−N2 N2−N3 N4−N5 N6−N7 N2−H2
2.001(6) 2.022(5) 2.056(5)
2.052 2.045 2.097
2.030(6) 2.039(6) 2.032(6)
2.049 2.082 2.091
2.024(7) 2.029(6)
2.046 2.091
2.000(3) 2.003(3) 2.058(4)
2.044 2.045 2.101
2.072(6)
2.175
2.091(5) 2.052(5) 2.082(6) 1.265(6) 1.265(6) 1.413(9)
2.130 2.133 2.103 1.256 1.258 1.423
2.045(5) 2.007(5) 2.080(5) 1.260(8)
2.130 2.103 2.098 1.250
1.425(11)
1.442
2.090(3) 2.084(3) 2.049(4) 1.271(4) 1.260(4) 1.397(6)
2.168 2.170 2.103 1.256 1.256 1.417
1.389(7) 1.377(8)
1.386 1.386
1.363(9) 1.309(10)
1.371 1.331
1.381(5) 1.392(6)
1.387 1.388
1.287(7) 1.268(7)
1.274 1.274
1.294(8) 1.282(8) 1.00(6)
1.278 1.276
1.274(5) 1.278(5)
1.272 1.272
1.256(10)
1.249
1.43(3) 1.336(15)
1.422 1.386
1.282(8)
1.272
Scheme 3. Important Bond Distances
N(azo) distance (2.029(6) Å) compared to Ru−N(pyridine) distance (2.072(6) Å) in ct-3a+ due to the cis-orientation of Ru−N(azo) and Ru−NO(L). Accordingly, in case of NO,NH (L′−) derived 2+, the RuII− N(azo) distance (2.045(5) Å) trans to Ru-NO(L′−) is longer compared to RuII−N(azo) distance (2.007(5) Å) trans to RuNH(L′−). 1,2-Dinitrosobenzene (L) in tc-1+ and in isomeric ct-3a+, tc3b+ can in principle exist either in neutral L0 (N−O: 1.23−1.26 Å) or intermediate radical anionic L•− (N−O: 1.26−1.31 Å) or further reduced dianionic L2− (N−O: > 1.31 Å) state (Chart 2) with distinctive bond parameters.14a,17 A direct comparison of bond distances involving Ru−L fragment in tc-1+, ct-3a+, and tc3b+ with the reported [Ru(bpy)2(L)]+ (4+)17 (Scheme 3) ascertains its anionic radical state. This has further been corroborated by their free-radical electron paramagnetic
[3b]ClO4 of 168.8(2)°, 168.1(2)°, 172.5(3)°, and 164.72(14)°, respectively, are suggestive of distorted octahedral situation in each case. The tc configuration of the precursor {Ru(pap)2}20 maintains in 1+ and 2+. The structural analysis of [3a]ClO4 and [3b]ClO4 confirm their ct and tc isomeric forms with respect to pyridine and azo nitrogens of 2,6-dichloropap, respectively. The average azo distance of pap/2,6-dichloropap of 1.283(7)/1.279(6) Å in the complexes suggests its neutral (NN)0 state.25 The lengthening of NN distance in the complexes with respect to that in free pap (1.258(5) Å)26 implies dπ(RuII) → π*(NN) back-bonding.20 Comparable or longer average Ru−N(azo) distance (2.071(5)/2.087(3) Å) with respect to Ru−N(pyridine) distance (2.069(6)/ 2.054(4)Å) in tc-1+/tc-3b+ is a reflection of competitive backbonding scenario between RuII−N(azo) trans to RuII−NO(L). This has been further supported by the smaller average Ru− D
DOI: 10.1021/acs.inorgchem.6b02197 Inorg. Chem. XXXX, XXX, XXX−XXX
Article
Inorganic Chemistry
values at the intermediate states (Kc2−Kc4). Further, stronger πacceptor feature of pap18 in 1+ with respect to bpy in analogous 4+ 17 has been reflected in appreciably anodic-shifted O1 potential in the former (0.6 V (1+) versus 0.25 V (4+)). Under identical experimental set up, L′ derived tc-2+ displays reversible one oxidation (O1) and three successive reductions (R1−R3; Figure 5, Table 2), where oxidation and reduction processes are appreciably positive- and negative-shifted, respectively, as compared to the corresponding tc-1+, leading to a huge difference in Kc1 (O1/R1) value of 1022 (2+) versus 1011 (1+). In agreement with L•−-dominated spin (Figure 6 and Table 3; see also Figure S5 and Table S7 in the Supporting
resonance (EPR) spectra (see later) as well as broad paramagnetic 1H NMR feature. The evaluation of bond parameters of mono-anionic L′− in + 2 (Scheme 3) with those in reported analogous [TpRuIICl{N(O)C5H3-tBu-NH-κ2-N,N}, Tp = hydridotris(pyrazolyl) borate)],22 reveals the delocalization of negative charge over the HN−C−C−N(O) centers. The experimental (X-ray) bond parameters in each case are well-reproduced by density functional theory (DFT) calculations (Table 1 and Tables S2 and S3, Figure S4 in the Supporting Information). Electrochemistry, Electron Paramagnetic Resonance, Electronic Spectra, and Electronic Structural Aspects. The radical complexes [RuII(pap)2)L•−]+ (tc-1+) and isomeric [RuII(2,6-dichloropap)2)L•−]+ (ct-3a+, tc-3b+) exhibit reversible one oxidation (O1) and three to four stepwise reduction processes (R1−R3/R4) within the potential window of ±2 V versus saturated calomel reference electrode (SCE) in CH3CN (Figure 5 and Table 2). The potential varies appreciably based
Figure 6. DFT-calculated Mulliken spin density plots for the paramagnetic forms of 1n and 2n.
Table 3. DFT-Calculated Mulliken Spin Distributions for 1n and 2n complex
Ru
1 (S = 1/2) 1 (S = 1) (ES=0 − ES=1 = 2098 cm−1) 1− (S = 3/2), (ES=1/2 − ES=3/2 = 631 cm−1) 2− 1 (S = 1), (ES=2 − ES=1 = 2168 cm−1) 2+ 2 (S = 1/2) 2 (S = 1/2) 2− (S = 1), (ES=0 − E1 = 2620 cm−1) 2− 2 (S = 1/2), (ES=3/2 − E1/2 = 1396 cm−1)
−0.044 −0.217
1.04 1.102
0.008 1.117 (0.595, 0.522)
−0.016
1.178
1.716 (0.919,0.797)
0.056 (1.133, − 1.057) 0.648 0.01 0.054
1.725 (0.973,0.752) 0.003 1.161 (0.483,0.678) 1.828 (0.914,0.914)
−0.588
1.159 (0.553,0.606)
+
Figure 5. Cyclic voltammograms (black) and differential pulse voltammograms (green) of (a) [1]ClO4, (b) [2]ClO4, (c) [3a]ClO4, and (d) [3b]ClO4 in CH3CN.
on the effect of substitution in the pap framework as well as isomeric configuration. Notably, oxidation (O1) and first two reduction (R1 and R2) processes of isomeric ct-3a+ and tc-3b+ are appreciably positive-shifted with respect to tc-1+ due to the impact of electron-withdrawing Cl groups in the pap framework. Though isomeric ct-3a+ and tc-3b+ exhibit identical O1, significant difference in reduction potentials is apparent, which in effect lead to varying comproportionation constant (Kc)
L/L′
0.325 0.364 −0.161 0.113 0.429
pap
Table 2. Redox Potentials and Comproportionation Constants E°298/V (ΔE/mV)a,b complex
Kcc R4
Kc1c
Kc2c
Kc3c
Kc4c
O1
R1
R2
R3
+
tc-1
0.60 (60)
−0.09 (60)
−0.59 (60)
−1.10 (60)
4.95 × 10
tc-2+
0.93 (70)
−0.40 (60)
−0.88 (60)
−1.57 (100)
3.49 × 1022
1.31 × 108
1.04 × 1013
ct-3a+
0.66 (60)
−0.07 (60)
−0.22 (60)
−0.50 (60)
−0.81 (90)
2.36 × 1012
3.49 × 102
5.57 × 104
1.80 × 105
tc-3b+
0.66 (70)
−0.05 (60)
−0.46 (60)
−1.20 (65)
−1.76 (150)
1.08 × 1012
8.90 × 106
3.63 × 1012
3.10 × 109
4+
0.25
−0.48
11
2.35 × 1012
2.98 × 10
8
4.41 × 10
8
ref this work this work this work this work 17
From cyclic voltammetry in CH3CN/0.1 M Et4N+ClO4− for 1+, 2+, 3a+, 3b+ and 0.1 M CH3CN/Et4N+PF6− for 4+, scan rate 100 mV s−1. bPotential in volts versus SCE; peak potential differences ΔEp/mV (in parentheses). cComproportionation constant from RT ln Kc = nF(ΔE).28 Kc1 between O1 and R1, Kc2 between R1 and R2, Kc3 between R2 and R3, and Kc4 between R3 and R4. a
E
DOI: 10.1021/acs.inorgchem.6b02197 Inorg. Chem. XXXX, XXX, XXX−XXX
Article
Inorganic Chemistry Information), the complexes tc-1+, ct-3a+, and tc-3b+ display free-radical EPR (g ≈ 2)27 in acetonitrile at 100 K (Figure 7, Table 4, and Figure S6 in the Supporting Information). The nitrogen hyperfine splitting (I(14N) = 1, A: 17 G)11a,14c was partly resolved in 3b+.
Figure 7. EPR spectra of 22+ (S = 1/2), 2 (S = 1/2), 3b+ (S = 1/2), and 3b (S = 1) in CH3CN at 100 K.
Table 4. EPR Data in CH3CN at 100 K complex
g1/2
giso
not resolved
2.012 1.993
+
1 (S = 1/2) 1 (S = 1) 22+ (S = 1/2) 2 (S = 1/2) 3a+ (S = 1/2) 3a (S = 1) 3b+ (S = 1/2) 3b (S = 1)
⟨g⟩a
Figure 8. UV−vis−NIR spectra of (a) 1+, 3a+, 3b+ (insets) fragmented spectral features, (b) 1n (inset) fragmented spectral feature, and (c) 2n. 2.041
not resolved 3.781
Δgb
0.061
[RuIII(pap)2L′−]2+ (minor).1f,h This has further been substantiated by the radical-based EPR (⟨g⟩: 2.041, Δg: 0.061)29 with partial metal-based anisotropic feature as well as by Mulliken spin distribution in 22+. The redox noninnocent potential of coordinated L has also been documented earlier in [Ru(bpy)2(L)]n (4n)/[Ru([9]aneS3)(L)]n;17 the present article, however, demonstrating the noninnocence of L′ for the first time in selective molecular framework of 2n. The presence of easily reducible pap derivative with diagnostic N−N (azo) distances [(NN)0 < 1.30 Å, (N N)•− ≥ 1.33 Å, (NN)2− ≥ 1.40 Å]4b,7 along with the potential redox-active L or L′ (Chart 2) in the complexes brings into a rather competitive scenario with special reference to their involvement in the successive reduction processes in Figure 5 (Table 2). A critical review of experimental and DFT results reveals the involvement of low-lying close by π*-LUMOs of two pap or 2,6-dichloropap units in initial uptake of two electrons (R1 and R2 in Figure 5), resulting in S = 1 (1,3) and S = 3/2 (↑↑↑) (1−)/S = 1/2 (↑↓↑) (3−) states. The triplet S = 1 state in 1 or 3 exhibits free-radical EPR at g ≈ 2 along with the characteristic forbidden half-field signature at g ≈ 4 at 100 K in case of 3b.30 The DFT results also suggest that the third electron (R3 in Figure 5) is moving into L•− but in opposite spin, which in effect leaves two parallel spins (S = 1) in two pap units in 12−, 32−, implying the bidirectional noninnocent feature of L (L0 ← L•− → L2−) in the newly designed coordination situations in 1n, 3n. The introduction of fourth electron in 3+
1.993 2.006 2.003 2.008 1.996
⟨g⟩ = {1/3(g12 + g22 + g32)}1/2 (g1: 2.077, g2: 2.031, g3: 2.016). bΔg = g1 − g3. a
The pertaining question of selective involvement of Ru (Ru(II)→Ru(III)) or L/L′ (Chart 2) based frontier orbitals in the oxidation (O1) process of 1+, 3+/2+, respectively, was ascertained by DFT-calculated spin-density plots (Figure 6, Table 3, and Figure S5, Table S7 in the Supporting Information), molecular orbital (MO) compositions (Tables S8−S36 in the Supporting Information), EPR (Figure 7, Table 4, and Figure S6 in the Supporting Information), UV−vis−NIR (Figures 8, S7, and S8 and Tables S37−S38 in the Supporting Information), and IR (Figure S9 in the Supporting Information) spectral features. The L•−-based singly occupied molecular orbital (SOMO) of + 1 , 3+ and lowest unoccupied molecular orbital (LUMO) of 12+, 32+, however, clearly suggest its oxidation to L0 state, leading to an EPR-inactive [RuII(pap)2(L0)]2+ configuration for the oxidized (O1) state instead of the alternate spin coupled [RuIII(pap)2(L•−)]2+ form. However, L′-dominated MOs with partial metal contribution in 2+ and 22+ extend the notion of a resonating form of [RuII(pap)2L′•]2+ (major)/ F
DOI: 10.1021/acs.inorgchem.6b02197 Inorg. Chem. XXXX, XXX, XXX−XXX
Article
Inorganic Chemistry Scheme 4. Electronic Structural Formsa of 1n/3n and 2n
a
pap = pap or 2,6-dichloropap.
1100−1300 nm, involving SOMO of L•− and the vacant π* LUMO of pap.33 The intense visible and UV bands are originated via pap or L targeted mixed metal−ligand and intra/ interligand transitions, respectively. Moreover, visible bands vary appreciably in terms of both band position and intensity as a function of substituents in the framework of pap (1+ versus 3+) as well as isomeric identities of 3a+ and 3b+. In agreement with the electronic structural forms as discussed above, the radical-based near-IR band in 1 + disappears on one-electron oxidation to [RuII(pap)2(L0)]2+ (12+). On the one hand, oxidized 12+ displays L targeted metal−ligand to ligand charge transfer transition in the visible region in addition to primarily ligand-based bands in the higher-energy UV-region. On the other hand, one-electron reduced diradical state [RuII(pap•−)(pap)(L•−)] (S = 1) in 1 exhibits weak near-IR absorptions at 1650 and 900 nm corresponding to L targeted ligand to ligand−metal and ligand−metal to ligand−metal charge-transfer transitions, respectively. The higher-energy multiple transitions covering visible to UV region originate through L or pap targeted mixed metal−ligand and intra/interligand charge transfer transitions. Interestingly, the lowest-energy visible band of 1+ moves to the lower-energy red region on oxidation or reduction: 1+ (507 nm) > 12+ (567 nm) > 1 (575 nm). The L′ ligand derived [RuII(pap)2(L′−)]+ (2+) displays one weak low-energy band at 907 nm and multiple intense bands in the visible to UV region corresponding to pap or L′ targeted mixed metal−ligand and ligand derived transitions. Oneelectron oxidized [RuII(pap)2(L′•)]2+/[RuIII(pap)2(L′−)]2+ (22+) exhibits two low-energy absorptions at 1611 and 1030 nm in addition to higher-energy bands that are assigned to mixed ligand−metal charge transfer transitions. The 1611 nm band of 22+ failed to reproduce at the present level of calculations; however, ((U)PBEPBE/CPCM/CH3CN) level of calculations predicts the nearest very weak absorption at 1379 nm (f = 0.001). The one-electron reduced [RuII(pap•−)(pap)(L′−)] (2) radical species also displays two low-energy transitions at 1800 and 1004 nm, which essentially represent pap to pap and pap to L′ derived transitions. The visible and
(R4, Figure 5) exhibits a complex spin distribution pattern over all the entities in different extent. The initial successive two-electron uptake processes by two pap units in 2+ led to an uncoupled S = 1 state in 2− (R2 in Figure 5) via the S = 1/2 state in intermediate 2 (R1 in Figure 5) with a spin hopping situation between the two pap units (Table 2, Figure 6).31 This was further supported by the freeradical EPR of 2 at 100 K. The uptake of third electron (R3 in Figure 5) results in an S = 1/2 state in 22− with a complex spin distribution pattern involving positive and negative spins on Ru/pap and L′, respectively, leading to a resonating electronic configuration of [RuII(pap•−)2(L′•2−)]2−/ [RuIII(pap•−)2(L′3−)]2− (RIET = redox induced electron transfer process32). Thus, like L in 1n, 3n, participation of L′ orbitals both in oxidation and reduction processes was realized for the first time in selective molecular framework of 2n. The calculated systematic change in redox-sensitive NN (azo, pap, or 2,6-dichloropap) and NO (L or L′) bond distances in the complexes on oxidation or reduction process (Table S39 in the Supporting Information) is also well in agreement. Thus, N−O distance of L or L′ decreases and increases on oxidation and reduction, respectively, while gradual lengthening of NN distance takes place on successive electron uptake processes. The L-based oxidation and pap-based first reduction of 1+ was further ascertained by monitoring the characteristic change in ν(NO)17 and ν(NN, pap)7e vibrations on electron transfer processes, where ν(NO) frequency increases from 1245 to 1366 cm−1 on oxidation to 12+ and ν(NN, pap) frequency of one of the pap units decreases from 1305 to 1148 cm−1 on reduction to 1 (Figure S9 in the Supporting Information). The spectral features of the complexes in native (1+, 2+, 3+) and coulometrically generated reversible redox states of representative 1n and 2n (n = 2+, +, 0) are shown in Figure 8 and Figures S7, S8, Tables S37, S38 in the Supporting Information). The transitions are assigned based on the TDDFT calculations, which match reasonably well with the experiments. The radical complexes [RuII(pap)2(L•−)]+, 1+, and isomeric 3+ exhibit a weak and broad near-IR band in the range of G
DOI: 10.1021/acs.inorgchem.6b02197 Inorg. Chem. XXXX, XXX, XXX−XXX
Article
Inorganic Chemistry
(282001.00081) spectrometer. IR spectra of the complexes as KBr pellets were recorded on a Nicolet spectro-photometer. Preparation of Complexes. Synthesis of ccc-RuII(2,6-dichloropap)2Cl2 and tcc-RuII(2,6-dichloropap)2Cl2. Ru(DMSO)4Cl2 (500 mg, 1.19 mmol; DMSO = dimethyl sulfoxide) and 2,6-dichloropap (600 mg, 2.38 mmol) were taken in 150 mL of acetone in a 250 mL round bottomed flask. The mixture was heated to reflux with stirring for 18 h. The color of the reaction mixture gradually changed to dark blue-violet. The solvent was removed under reduced pressure. The crude product was purified on a neutral alumina column, which led to the initial elution of the blue complex by 12:1 CH2Cl2−CH3CN, followed by the blue-violet complex by 1:2 CH2Cl2−CH3CN corresponding to tcc-RuII(2,6-dichloropap)2Cl2 and ccc-RuII(2,6dichloropap)2Cl2, respectively. Evaporation of solvent under reduced pressure yielded the pure complexes in the solid form. The structural and spectral items are set in Supporting Information (Figures S10− S12 and Table S40 in the Supporting Information). tcc-RuII(2,6-dichloropap)2Cl2. Yield, 302 mg (36%). 1H NMR in CDCl3 [δ, ppm (J, Hz)]: 8.81 (d, 5.2, 1H), 8.55 (d, 8.0, 1H), 8.21 (t, 6.0, 1H), 7.91 (t, 6.0, 1H), 7.07 (t, 3.0, 3H). MS (ESI+, CH3CN): m/z {[M-Cl]}+ calcd: 640.87; found: 640.89. Molar conductivity (MeCN): Λ M = 7 Ω −1 cm 2 M −1 . Elemental analysis calcd (%) for C22H14N6Cl6Ru: C, 39.08; H, 2.09; N, 12.43; found: C, 38.84; H, 1.95; N, 12.61. ccc-RuII(2,6-dichloropap)2Cl2. Yield, 462 mg (55%). 1H NMR in CDCl3 [δ, ppm (J, Hz)]: 9.96 (d, 5.5, 1H), 8.61 (m, 2H), 8.20 (t, 7.8, 1H), 8.01 (t, 7.7, 1H), 7.89 (t, 6.7, 1H), 7.54 (d, 8.5, 1H), 7.44 (d, 5.5, 1H), 7.40 (t, 6.5, 1H), 7.33 (m, 8.5, 2H), 7.25 (d, 5.5, 1H), 7.21 (t, 6.5, 1H), 7.05 (t, 6.5, 1H). MS (ESI+, CH3CN): m/z {[M-Cl]}+ calcd: 640.87; found: 640.84. Molar conductivity (CH3CN): ΛM = 11 Ω−1 cm2 M−1. Elemental analysis calcd (%) for C22H14N6Cl2Ru: C, 39.08; H, 2.09; N, 12.43; found: C, 39.37; H, 1.99; N, 12.11. Synthesis of tc-[RuII(pap)2(L)]ClO4, [1]ClO4 and tc-[RuII(pap)2(L′)]ClO4, [2]ClO4. The precursor complex ctc-Ru(pap)2Cl2 (100 mg, 0.19 mmol) in 75 mL of ethanol was refluxed with silver perchlorate (87 mg, 0.42 mmol) for 2 h. The initial dark blue mixture gradually changed to reddish-violet. The precipitated AgCl was filtered off and washed with cold ethanol. Benzofuroxan (46.5 mg, 0.34 mmol) was then added to the above filtrate and heated at reflux for 14 h under dinitrogen atmosphere, which led to a brown solution. The solvent was removed under reduced pressure. The crude product was purified on a neutral alumina column, which eluted reddish-brown solution of [1]ClO4 by 10:1 CH2Cl2−CH3CN, followed by the brown solution of [2]ClO4 by 5:1 CH2Cl2−CH3CN. Evaporation of solvent under reduced pressure yielded [1]ClO4 and [2]ClO4 in the solid form. [1]ClO4. Yield, 54 mg (61%). MS (ESI+, CH3CN): m/z {[M]+} calcd: 604.07; found: 604.08. IR (KBr; cm−1): ν(NO): 1245, ν(ClO4−): 1087, 621. Molar conductivity (CH3CN): ΛM = 122 Ω−1 cm2 M−1. Elemental analysis calcd (%) for C28H22N8O6ClRu: C, 47.84; H, 3.15; N, 15.94; found: C, 48.08; H, 3.25; N, 15.74. [2]ClO4. Yield, 20 mg (22%). 1H NMR in CDCl3 [δ/ppm (J/Hz)]: 9.57 (S, 1H, NH), 8.63 (d, 8.0, 1H), 8.53 (d, 8.0, 1H), 8.41 (d, 4.8, 1H), 8.01 (t, 6.8, 7.4, 2H), 7.93 (d, 4.8, 1H), 7.56 (t, 5.6, 1H), 7.35 (m, 3H), 7.24 (d, 7.6, 2H), 7.18 (t, 8.0, 3H), 7.13 (d, 8.0, 2H), 6.99 (d, 7.2, 2H), 6.89 (d, 8.4, 1H), 6.81 (m, 1H), 6.27 (m, 1H) MS (ESI+, MeCN): m/z {[M]+} calcd: 589.11; found: 589.10. IR (KBr; cm−1): ν(NH): 3418 ν(NO):1253, ν(ClO4−): 1088, 621. Molar conductivity (CH3CN): ΛM = 108 Ω−1 cm2 M−1. Elemental analysis calcd (%) for C28H23N8O5ClRu: C, 48.88; H, 3.37; N, 16.29; found: C, 48.69; H, 3.27; N, 16.39. Synthesis of ct-[RuII(2,6-dichloropap)2(L)]ClO4, [3a]ClO4 and tc[RuII(2,6-dichloropap)2(L)]ClO4, [3b]ClO4. The precursor complex ccc[Ru(2,6-dichloropap)2Cl2] (100 mg, 0.15 mmol) in 75 mL of ethanol was refluxed with silver perchlorate (85 mg, 0.31 mmol) for 2 h. The initial blue mixture gradually changed to violet. The precipitated AgCl was filtered off and washed with cold ethanol. Benzofuroxan (36.74 mg, 0.27 mmol) was added to the filtrate and heated at reflux for 16 h under dinitrogen atmosphere. The initial violet color changed to brown. The solvent was removed under reduced pressure. The crude product was purified on a neutral alumina column, which led to the
UV absorptions correspond to mixed metal/ligand and ligand based charge transfer transitions, respectively. On the basis of the aforesaid experimental and DFT deliberations an outline of the electronic structural forms in different redox states of the complexes is depicted in Scheme 4.
■
CONCLUSION Following are the salient features of the article: Simultaneous formation of the radical ([Ru(pap)2(L•−)]+, + 1 ) and nonradical ([Ru(pap)2(L′−)]+, 2+) complexes was achieved via the reaction of {Ru(pap)2} metal precursor and benzofuroxan. L and L′− constitute the in situ generated 1,2dinitrosobenzene, an intermediate tautomeric form of the biologically active benzofuroxan16 and 2-nitrosoanilido, respectively. Though the isomeric identity of tc-{Ru(pap)2} precursor has been retained in tc-1+ and tc-2+, the introduction of cc-{Ru(2,6dichloropap)2} metal precursor generates isomeric ct-[Ru(2,6dichloropap) 2 (L •− )] + (3a + ) and tc-[Ru(2,6-dichloropap)2(L•−)]+ (3b+) (cc or ct or tc orientation of pyridine and azo nitrogens of 2,6-dichloropap, respectively) with the unusual change in configuration20 of the precursor. Strikingly, ctisomeric form of {Ru(2,6-dichloropap)2} in 3a+ embodies structural authentication of previously considered thermodynamically unstable form of {Ru(pap)2} family.19,24 The participation of L and L′− based frontier orbitals in both the oxidation and reduction processes of 1n, 3n, and 2n, respectively, implies their bidirectional noninnocent potential. The impact of π-accepting pap has indeed facilitated the invariant Ru(II) state along the redox chain of the complexes as well as introduced a competitive reduction scenario between its azo(NN) function and nitroso group of L or L′. Reemphasizing and recognition of the redox-noninnocent potential of L and L′ in a selected molecular setup of 1n, 3n, and 2n, respectively, including the unusual isomeric identity of {Ru(pap)2} family, would introduce a new dimension/impetus for further exploration with more challenging molecular frameworks.
■
EXPERIMENTAL SECTION
Materials. The precursor metal complex ctc-RuII(pap)2Cl234 was prepared according to the reported procedure. Benzofuroxan was purchased from Sigma-Aldrich. All other chemicals and reagents were reagent grade and were used as received. For spectroscopic and electrochemical studies HPLC-grade solvents were used. Physical Measurements. The electrical conductivities of the complexes in CH3CN were checked with autoranging conductivity meter (Toshcon Industries, India). 1H NMR spectra were recorded using a Bruker Avance III 400 MHz spectrometer. The elemental analysis was performed on a Thermoquest (EA 1112) microanalyzer. Cyclic voltammetry measurements were performed on a PAR model 273A electrochemistry system. A glassy carbon working electrode, a platinum wire auxiliary electrode, and an SCE were used in a standard three-electrode configuration. A platinum wire-gauze working electrode was used for the constant potential coulometry experiment. Tetraethylammonium perchlorate was used as the supporting electrolyte, and the solute concentration was ∼1 × 10−3 M. The scan rate used was 100 mVs−1. All electrochemical experiments were performed under dinitrogen atmosphere. The half-wave potential E°298 was set equal to 0.5(Epa + Epc), where Epa and Epc are anodic and cathodic cyclic voltammetry peak potentials, respectively. The EPR measurements were made on Bruker EMX Plus at 100 K (liquid N2). UV−vis−NIR spectral studies were performed on a PerkinElmer Lambda 1050 spectro-photometer. Electrospray ionization (ESI) mass spectrometry (MS) was checked on a Bruker’s Maxis Impact H
DOI: 10.1021/acs.inorgchem.6b02197 Inorg. Chem. XXXX, XXX, XXX−XXX
Article
Inorganic Chemistry initial elution of the brown complex [3b]ClO4 by 9:1 CH2Cl2− CH3CN, followed by the reddish-brown complex [3a]ClO4 by 8:1 CH2Cl2−CH3CN. Evaporation of solvent under reduced pressure yielded the pure complexes [3a]ClO4 and [3b]ClO4. [3a]ClO4. Yield, 83 mg (67%). MS (ESI+, CH3CN): m/z {[M]+} calcd: 741.937; found: 741.923. IR (KBr; cm−1): ν(NO):1256, ν(ClO4−): 1085, 619. Molar conductivity (CH3CN): ΛM = 93 Ω−1 cm2 M−1. Elemental analysis calcd (%) for C28H18Cl5N8O6Ru: C, 40.00; H, 2.16; N, 13.33; found: C, 40.23; H, 1.97; N, 13.11. [3b]ClO4. Yield, 22 mg (20%). MS (ESI+, CH3CN): m/z {[M]+} calcd: 741.937; found: 741.922. IR (KBr; cm−1): ν(NO):1245, ν(ClO4−): 1087, 621. Molar conductivity (CH3CN): ΛM = 105 Ω−1 cm2 M−1. Elemental analysis calcd (%) for C28H18Cl5N8O6Ru: C, 40.00; H, 2.16; N, 13.33; found: C, 40.31; H, 2.10; N, 13.48. Caution! Perchlorate salts are explosive and should be handled with care. Crystal Structure Determination. Single crystals of [1]ClO4, [2] ClO4, [3a]ClO4, [3b]ClO4, ccc-RuII(2,6-dichloropap)2Cl2, and tccRuII(2,6-dichloropap)2Cl2 were grown by slow evaporation of their 1:1 dichloromethane−benzene, 2:1 acetonitrile−benzene, 3:2 dichloromethane−benzene, 1:1 dichloromethane−benzene, 1:1 dichloromethane−hexane, and 1:1 chloroform−toluene, respectively. The Xray crystal data were collected on a RIGAKU SATURN-724+ CCD single-crystal X-ray diffractometer. The data were collected by the standard omega scan technique and were scaled and reduced using the CrystalClear-SM Expert software. The structures were solved by direct method using SHELXS-97 and refined by full matrix least-squares with SHELXL-2014, refining on F2.35 All non-hydrogen atoms were refined anisotropically. The remaining hydrogen atoms except (N−H) of [2]ClO4 were placed in geometrically constrained positions and refined with isotropic temperature factors, generally 1.2Ueq of their parent atoms. Hydrogen atoms were included in the refinement process as per the riding model. The disordered solvent molecules in [1]ClO4 and [3a]ClO4 were SQUEEZE by PLATON36 program. Supplementary crystallographic data for the compounds in this paper have been provided by the Cambridge Crystallographic Data Centre (CCDC; https://www.ccdc.cam.ac.uk/structures-beta/): CCDC No. 1503496 ([1]ClO4), CCDC No. 1503497 ([2]ClO4), CCDC No. 1503498 ([3a]ClO4), CCDC No. 1503499 ([3b]ClO4), CCDC No. 1503500 (ccc-Ru(2,6-dichloropap)2Cl2), and CCDC No. 1503501 (tcc-Ru(2,6-dichloropap)2Cl2). Computational Details. Full geometry optimizations were performed by using the DFT method at the (R)B3LYP level for 12+, 2+, 3a2+, 3b2+, and 3b2− and at the (U)B3LYP level for 1+, 1, 1−, 12−, 22+, 2−, 22−, 3a+, 3a, 3a−, 3a2−, 3a3−, 3b+, 3b, 3b−, 3b2−, and 3b3−.37 Except ruthenium all other elements were assigned the 6-31G** basis set. The LANL2DZ basis set with effective core potential was employed for the ruthenium atom.38 The vibrational frequency calculations were performed to ensure that the optimized geometries represent the local minima, and there are only positive Eigen values. All calculations were performed with Gaussian09 program package.39 Vertical electronic excitations based on (R)B3LYP/(U)B3LYP optimized geometries were computed for 1n (n = 2+, +, 0), 2n (n = 2+, +, 0), 3a+, and 3b+ using the TD-DFT formalism40 in acetonitrile using conductor-like polarizable continuum model (CPCM).41 Chemissian 1.742 was used to calculate the fractional contributions of various groups to each molecular orbital. All calculated structures were visualized with ChemCraft.43 Electronic spectra were calculated using the SWizard program.44,45 TD-DFT of 22+(S = 1/2) was also tested using PBE46 function.
■
■
NMR spectra of 1+, 2+, ccc-Ru(2,6-dichloropap)2Cl2, and tcc-Ru(2,6-dichloropap)2Cl2; UV−vis−NIR spectra of 1n, 2n, 3a+, and 3b+; DFT-optimized structures of 1+, 2+, 3a+, and 3b+; EPR spectra of 1+, 1, 3a+, and 3a; spin density figures and table of 3an and 3bn; UV−vis−NIR spectra, ORTEP diagrams of ccc-Ru(2,6-dichloropap)2Cl2 and tccRu(2,6-dichloropap)2Cl2; MO compositions of 1n, 2n, 3an, and 3bn (PDF) X-ray crystallographic files in CIF format for [1]ClO4 (CIF) X-ray crystallographic files in CIF format for [2]ClO4 (CIF) X-ray crystallographic files in CIF format for [3a]ClO4 (CIF) X-ray crystallographic files in CIF format for [3b]ClO4 (CIF) X-ray crystallographic files in CIF format for ccc-Ru(2,6dichloropap)2Cl2 (CIF) X-ray crystallographic files in CIF format for tcc-Ru(2,6dichloropap)2Cl2 (CIF)
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Goutam Kumar Lahiri: 0000-0002-0199-6132 Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS Financial support received from the Department of Science and Technology, Council of Scientific and Industrial Research (fellowship to P.G.), New Delhi (India), is gratefully acknowledged.
■
REFERENCES
(1) (a) Hazari, A. S.; Das, A.; Ray, R.; Agarwala, H.; Maji, S.; Mobin, S. M.; Lahiri, G. K. Tunable Electrochemical and Catalytic Features of BIAN- and BIAO Derived Ruthenium Complexes. Inorg. Chem. 2015, 54, 4998−5012. (b) Hazari, A. S.; Ray, R.; Hoque, M. A.; Lahiri, G. K. Electronic Structure and Multicatalytic Features of Redox-Active Bis(arylimino)acenaphthene (BIAN)-Derived Ruthenium Complexes. Inorg. Chem. 2016, 55, 8160−8173. (c) Ghosh, P.; Mondal, P.; Ray, R.; Das, A.; Bag, S.; Mobin, S. M.; Lahiri, G. K. Significant Influence of Coligands Toward Varying Coordination Modes of 2,2′-Bipyridine3,3′-diol in Ruthenium Complexes. Inorg. Chem. 2014, 53, 6094−6106. (d) Ghosh, P.; Ray, R.; Das, A.; Lahiri, G. K. Revelation of Varying Coordination Modes and Noninnocence of Deprotonated 2,2′Bipyridine-3,3′-diol in {Os(bpy)2} Frameworks. Inorg. Chem. 2014, 53, 10695−10707. (e) Ghosh, P.; Lahiri, G. K. Impact of {Os(pap)2} in Fine-Tuning the Binding Modes and Non-innocent Potential of Deprotonated 2,2′-Bipyridine-3,3′-diol. Dalton Trans. 2016, 45, 5240− 5252. (f) Mondal, P.; Das, A.; Lahiri, G. K. The Electron-Rich {Ru(acac)2} Directed Varying Configuration of the Deprotonated Indigo and Evidence for Its Bidirectional Noninnocence. Inorg. Chem. 2016, 55, 1208−1218. (g) Mondal, P.; Ray, R.; Das, A.; Lahiri, G. K. Revelation of Varying Bonding Motif of Alloxazine, a Flavin Analogue, in Selected Ruthenium(II/III) Frameworks. Inorg. Chem. 2015, 54, 3012−3021. (h) Ansari, M. A.; Mandal, A.; Paretzki, A.; Beyer, K.; Fiedler, J.; Kaim, W.; Lahiri, G. K. 1,5-Diamido-9,10-anthraquinone, a Centrosymmetric Redox-Active Bridge with Two Coupled β− Ketiminato Chelate Functions: Symmetric and Asymmetric Diruthenium Complexes. Inorg. Chem. 2016, 55, 5655−5670. (i) Das, A.; Mobin, S. M.; Lahiri, G. K. Recognition of Fractional Non-innocent
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.6b02197. Mass spectra, crystallographic parameters, bond lengths, and bond angles of 1+, 2+, 3a+, 3b+, ccc-Ru(2,6dichloropap)2Cl2, and tcc-Ru(2,6-dichloropap)2Cl2; 1H I
DOI: 10.1021/acs.inorgchem.6b02197 Inorg. Chem. XXXX, XXX, XXX−XXX
Article
Inorganic Chemistry Feature of Osmium Coordinated 2,2′-Biimidazole or 2,2′-bis(4,5dimethylimidazole) and their Interactions with Anions. Dalton Trans. 2015, 44, 13204−13219. (j) Das, A.; Mondal, P.; Dasgupta, M.; Kishore, N.; Lahiri, G. K. Substituent Directed Selectivity in Anion Recognition by a New class of Simple Osmium-pyrazole Derived Receptors. Dalton Trans. 2016, 45, 2605−2617. (k) Das, A.; Kundu, T.; Mobin, S. M.; Priego, J. L.; Jimenez-Aparicio, R.; Lahiri, G. K. Influence of Ancillary Ligands on the Electronic Structure and Anion Sensing Features of Ligand Bridged Diruthenium Complexes. Dalton Trans. 2013, 42, 13733−13746. (l) Das, A.; Agarwala, H.; Kundu, T.; Ghosh, P.; Mondal, S.; Mobin, S. M.; Lahiri, G. K. Electronic Structures and Selective Fluoride Sensing Features of Os(bpy)2(HL2−) and [{Os(bpy)2}2(μ-HL2−)]2+ (H3L: 5-(1H benzo[d]imidazol-2-yl)1H-imidazole- 4-carboxylic acid). Dalton Trans. 2014, 43, 13932− 13947. (m) Das, A.; Ghosh, P.; Plebst, S.; Schwederski, B.; Mobin, S. M.; Kaim, W.; Lahiri, G. K. Ancillary Ligand Control of Electronic Structure in o- Benzoquinonediimine-Ruthenium Complex Redox Series: Structures, Electron Paramagnetic Resonance (EPR), and Ultraviolet−Visible−Near-Infrared (UV-vis-NIR) Spectroelectrochemistry. Inorg. Chem. 2015, 54, 3376−3386. (n) Das, A.; Ghosh, P.; Priego, J. L.; Jimenez-Aparicio, R.; Lahiri, G. K. Unsymmetric (μoxido)/(μ-pyrazolato) and Symmetric (μ-pyrazolato)2 Bridged Diosmium Frameworks: Electronic Structure and Magnetic Properties. Inorg. Chem. 2016, 55, 8396−8406. (2) (a) Luca, O.; Crabtree, R. H. Redox-Active Ligands in Catalysis. Chem. Soc. Rev. 2013, 42, 1440−1459. (b) Wang, W.; Nilges, M. J.; Rauchfuss, T. B.; Stein, M. Isolation of a Mixed Valence Diiron Hydride: Evidence for a Spectator Hydride in Hydrogen Evolution Catalysis. J. Am. Chem. Soc. 2013, 135, 3633−3639. (c) Dzik, W. I.; van der Vlugt, J. I.; Reek, J. N. H.; de Bruin, B. Ligands that Store and Release Electrons during Catalysis. Angew. Chem., Int. Ed. 2011, 50, 3356−3358. (d) Chirik, P. J.; Wieghardt, K. Radical Ligands Confer Nobility on Base-Metal Catalysts. Science 2010, 327, 794−795. (e) Bart, S. C.; Lobkovsky, E.; Bill, E.; Chirik, P. J. Synthesis and Hydrogenation of Bis(imino)pyridine Iron Imides. J. Am. Chem. Soc. 2006, 128, 5302−5303. (f) Lyaskovskyy, V.; de Bruin, B. D. Redox Non-Innocent Ligands: Versatile New Tools to Control Catalytic Reactions. ACS Catal. 2012, 2, 270−279. (3) (a) Maji, S.; Sarkar, B.; Mobin, S. M.; Fiedler, J.; Urbanos, F. A.; Jimenez-Aparicio, R.; Kaim, W.; Lahiri, G. K. Valence-State Alternatives in Diastereoisomeric Complexes [(acac)2Ru(μ-QL)Ru(acac)2]n (QL2− = 1,4-Dioxido-9,10-anthraquinone, n = +2, +1, 0, −1, −2). Inorg. Chem. 2008, 47, 5204−5211. (b) Ernst, S.; Haenel, P.; Jordanov, J.; Kaim, W.; Kasack, V.; Roth, E. Stable Binuclear o- and pSemiquinone Complexes of [Ru(bpy)]2+. Radical Ion versus Mixed Valence Dimer Formulation. J. Am. Chem. Soc. 1989, 111, 1733−1738. (c) Joulie, L. F.; Schatz, E.; Ward, M. D.; Weber, F.; Yellowlees, L. J. Electrochemical Control of Bridging Ligand Conformation in a Binuclear Complex-A Possible Basis for a Molecular Switch. J. Chem. Soc., Dalton Trans. 1994, 799−804. (d) Delmedico, A.; Dodsworth, E. S.; Lever, A. B. P.; Pietro, W. J. Electronic Structure and Spectra of Linkage Isomers of Bis(bipyridine)(1,2-dihydroxy-9,10-anthraquinonato) ruthenium(II) and Their Redox Series. Inorg. Chem. 2004, 43, 2654−2671. (e) Pierpont, C. G. Ligand Redox Activity and Mixed Valency in First-Row Transition-Metal Complexes Containing Tetrachlorocatecholate and Radical Tetrachlorosemiquinonate Ligands. Inorg. Chem. 2011, 50, 9766−9772. (f) Girgis, A. Y.; Sohn, Y. S.; Balch, A. L. Preparation and Oxidation of Some Quinone Adducts of Transition Metal Complexes. Inorg. Chem. 1975, 14, 2327−2331. (4) (a) Kar, S.; Sarkar, B.; Ghumaan, S.; Janardanan, D.; van Slageren, J.; Fiedler, J.; Puranik, V. G.; Sunoj, R. B.; Kaim, W.; Lahiri, G. K. 2,5-Dioxido-1,4-benzoquinonediimine (H2L2−), A HydrogenBonding Noninnocent Bridging Ligand Related to Aminated Topaquinone: Different Oxidation State Distributions in Complexes [{(bpy)2Ru}2(μ-H2L)]n (n = 0, + , 2+, 3+, 4+) and [{(acac)2Ru}2(μH2L)]m (m = 2−, − , 0, + , 2+). Chem. - Eur. J. 2005, 11, 4901−4911. (b) Das, D.; Mondal, T. K.; Mobin, S. M.; Lahiri, G. K. Sensitive Valence Structures of [(pap)2Ru(Q)]n (n = + 2, + 1, 0, − 1, − 2) with Two Different Redox Noninnocent Ligands, Q = 3,5-Di-tert-butyl-N-
aryl-1,2-benzoquinonemonoimine and pap = 2-Phenylazopyridine. Inorg. Chem. 2009, 48, 9800−9810. (c) Bhattacharya, S.; Gupta, P.; Basuli, F.; Pierpont, C. G. Structural Systematics for o-C6H4XY Ligands with X,Y= O, NH, and S Donor Atoms. o-Iminoquinone and o-Iminothioquinone Complexes of Ruthenium and Osmium. Inorg. Chem. 2002, 41, 5810−5816. (d) Kokatam, S.; Weyhermuller, T.; Bothe, E.; Chaudhuri, P.; Wieghardt, K. Structural Characterization of Four Members of the Electron Transfer Series [PdII(L)2)2]n (L = oIminophenolate Derivative; n = 2−, 1−, 0, 1+, 2+). Ligand Mixed Valency in the Monocation and Monoanion with S = 1/2 Ground States. Inorg. Chem. 2005, 44, 3709−3717. (e) Chaudhuri, P.; Verani, C. N.; Bill, E.; Bothe, E.; Weyhermuller, T.; Wieghardt, K. Electronic Structure of Bis(o-iminobenzosemiquinonato)metal Complexes (Cu, Ni, Pd). The Art of Establishing Physical Oxidation States in Transition-Metal Complexes Containing Radical Ligands. J. Am. Chem. Soc. 2001, 123, 2213−2223. (5) (a) Skara, G.; Pinter, B.; Geerlings, P.; De Proft, D. Revealing the Thermodynamic Driving Force for Ligand-Based Reductions in Quinoids; Conceptual Rules for Designing Redox Active and Noninnocent Ligands. Chem. Sci. 2015, 6, 4109−4117. (b) Agarwala, H.; Ehret, F.; Chowdhury, A. D.; Maji, S.; Mobin, S. M.; Kaim, W.; Lahiri, G. K. Electronic Structure And Catalytic Aspects of [Ru(tpm) (bqdi) (Cl/H2O)]n, tpm = tris(1-pyrazolyl)-methane and bqdi = obenzoquinonediimine. Dalton Trans. 2013, 42, 3721−3734. (c) Maji, S.; Patra, S.; Chakraborty, S.; Janardanan, D.; Mobin, S. M.; Sunoj, R. B.; Lahiri, G. K. Valence-State Distribution in the Ruthenium oQuinonoid Systems [Ru(trpy) (Cl)(L1)]+ and [Ru(trpy) (Cl)(L2)]+ (L1 = o-Iminobenzoquinone, L2 = o- Diiminobenzoquinone; trpy = 2,2′: 6′,2//-Terpyridine). Eur. J. Inorg. Chem. 2007, 2007, 314−323. (d) Kalinina, D.; Dares, C.; Kaluarachchi, H.; Potvin, P. G.; Lever, A. B. P. Spectroscopic, Electrochemical, and Computational Aspects of the Charge Distribution in Ru(acac)2(R-o-benzoquinonediimine) Complexes. Inorg. Chem. 2008, 47, 10110−10126. (e) Rusanova, J.; Rusanov, E.; Gorelsky, S. I.; Christendat, D.; Popescu, R.; Farah, A. A.; Beaulac, R.; Reber, C.; Lever, A. B. P. The Very Covalent Diammino(o-benzoquinonediimine) Dichlororuthenium(II). An Example of Very Strong π-Back-Donation. Inorg. Chem. 2006, 45, 6246− 6262. (f) Metcalfe, R. A.; Vasconcellos, L. C. G.; Mirza, H.; Franco, D. W.; Lever, A. B. P. Synthesis and Characterization of Dinuclear Complexes of 3,3′,4,4′- Tetraminobiphenyl with Tetramminoruthenium and Bis(bipyridine)-ruthenium Residues and their two- and fourElectron Oxidized Products including a ZINDO Study of Orbital Mixing as a Function of Ligand Oxidation State. J. Chem. Soc., Dalton Trans. 1999, 2653−2667. (6) (a) Matz, K. G.; Mtei, R. P.; Leung, B.; Burgmayer, S. J. N.; Kirk, M. Noninnocent Dithiolene Ligands: A New Oxomolybdenum Complex Possessing a Donor-Acceptor Dithiolene Ligand. J. Am. Chem. Soc. 2010, 132, 7830−7831. (b) Schallenberg, D.; Neubauer, A.; Erdmann, E.; Tanzler, M.; Villinger, A.; Lochbrunner, S.; Seidel, W. W. Dinuclear Ru/Ni, Ir/Ni, and Ir/Pt Complexes with Bridging Phenanthroline-5,6-dithiolate: Synthesis, Structure, and Electrochemical and Photophysical Behavior. Inorg. Chem. 2014, 53, 8859−8873. (c) Sproules, S.; Banerjee, P.; Weyhermuller, T.; Yan, Y.; Donahue, J. P.; Wieghardt, K. Monoanionic Molybdenum and Tungsten Tris(dithiolene) Complexes: A Multifrequency EPR Study. Inorg. Chem. 2011, 50, 7106−7122. (7) (a) Kaim, W. Complexes with 2,2′-azobispyridine and related ‘Sframe’ bridging ligands containing the azo function. Coord. Chem. Rev. 2001, 219, 463−488. (b) Das, A.; Scherer, T. M.; Mobin, S. M.; Kaim, W.; Lahiri, G. K. Application of a Structure/Oxidation-State Correlation to Complexes of Bridging Azo Ligands. Chem. - Eur. J. 2012, 18, 11007−11018. (c) Sarkar, B.; Patra, S.; Fiedler, J.; Sunoj, R. B.; Janardanan, D.; Lahiri, G. K.; Kaim, W. Mixed-Valent Metals Bridged by a Radical Ligand: Fact or Fiction Based on StructureOxidation State Correlations. J. Am. Chem. Soc. 2008, 130, 3532−3542. (d) Sarkar, B.; Patra, S.; Fiedler, J.; Sunoj, R. B.; Janardanan, D.; Mobin, S. M.; Niemeyer, M.; Lahiri, G. K.; Kaim, W. Theoretical and Experimental Evidence for a New Kind of Spin-Coupled Singlet Species: Isomeric Mixed-Valent Complexes Bridged by a Radical J
DOI: 10.1021/acs.inorgchem.6b02197 Inorg. Chem. XXXX, XXX, XXX−XXX
Article
Inorganic Chemistry Anion Ligand. Angew. Chem., Int. Ed. 2005, 44, 5655−5658. (e) Paul, N.; Samanta, S.; Goswami, S. Redox Induced Electron Transfer in Doublet Azo-Anion Diradical Rhenium(II) Complexes. Characterization of Complete Electron Transfer Series. Inorg. Chem. 2010, 49, 2649−2655. (8) (a) Lahiri, G. K.; Kaim, W. Electronic Structure Alternatives in Nitrosylruthenium Complexes. Dalton Trans. 2010, 39, 4471−4478. (b) Kupper, C.; Rees, J. A.; Dechert, S.; DeBeer, S.; Meyer, F. Complete Series of {FeNO}8, {FeNO}7, and {FeNO}6 Complexes Stabilized by a Tetracarbene Macrocycle. J. Am. Chem. Soc. 2016, 138, 7888−7898. (c) Das, A. K.; Sarkar, B.; Duboc, C.; Strobel, S.; Fiedler, J.; Zalis, S.; Lahiri, G. K.; Kaim, W. An Odd-Electron Complex [Ruk(NOm)(Qn) (terpy)]2+ with Two Prototypical Non-Innocent Ligands. Angew. Chem., Int. Ed. 2009, 48, 4242−4245. (d) Roncaroli, F.; Videla, M.; Slep, L. D.; Olabe, J. A. New Features in the Redox Coordination Chemistry of Metal Nitrosyls {M−NO+; M−NO•; M− NO−(HNO)}. Coord. Chem. Rev. 2007, 251, 1903−1930. (e) Bari, S. E.; Marti, M. A.; Amorebieta, V. T.; Estrin, D. A.; Doctorovich, F. Fast Nitroxyl Trapping by Ferric Porphyrins. J. Am. Chem. Soc. 2003, 125, 15272−15273. (9) (a) Han, Y.; Wu, Y.; Lai, W.; Cao, R. Electrocatalytic Water Oxidation by a Water-Soluble Nickel Porphyrin Complex at Neutral pH with Low Overpotential. Inorg. Chem. 2015, 54, 5604−5613. (b) Wasylenko, D. J.; Rodriguez, C.; Pegis, M. L.; Mayer, J. M. Direct Comparison of Electrochemical and Spectrochemical Kinetics for Catalytic Oxygen Reduction. J. Am. Chem. Soc. 2014, 136, 12544− 12547. (c) Singh, P.; Das, A. K.; Sarkar, B.; Niemeyer, M.; Roncaroli, F.; Olabe, J. A.; Fiedler, J.; Zalis, S.; Kaim, W. Redox Properties of Ruthenium Nitrosyl Porphyrin Complexes with Different Axial Ligation: Structural, Spectroelectrochemical (IR, UV-Visible, and EPR), and Theoretical Studies. Inorg. Chem. 2008, 47, 7106−7113. (d) van Caemelbecke, E.; Derbin, A.; Hambright, P.; Garcia, R.; Doukkali, A.; Saoiabi, A.; Ohkubo, K.; Fukuzumi, S.; Kadish, K. M. Electrochemistry of [(TMpyP)MII]4+(X−)4 (X− = Cl− or BPh4−) and [(TMpyP)MIIICl]4+(Cl−)4 in N,N-Dimethylformamide Where M is One of 15 Different Metal Ions. Inorg. Chem. 2005, 44, 3789−3798. (10) (a) Mondal, P.; Ehret, F.; Bubrin, M.; Das, A.; Mobin, S. M.; Kaim, W.; Lahiri, G. K. A Diruthenium Complex of a “Nindigo” Ligand. Inorg. Chem. 2013, 52, 8467−8475. (b) Mondal, P.; Plebst, S.; Ray, R.; Mobin, S. M.; Kaim, W.; Lahiri, G. K. Uncommon cis Configuration of a Metal−Metal Bridging Noninnocent Nindigo Ligand. Inorg. Chem. 2014, 53, 9348−9356. (c) Nawn, G.; Waldie, K. M.; Oakley, S. R.; Peters, B. D.; Mandel, D.; Patrick, B. O.; McDonald, R.; Hicks, R. G. Redox-Active Bridging Ligands Based on Indigo Diimine (“Nindigo”) Derivatives. Inorg. Chem. 2011, 50, 9826−9837. (d) Oakley, S. R.; Nawn, G.; Waldie, K. M.; MacInnis, T. D.; Patrick, B. O.; Hicks, R. G. ‘‘Nindigo’’: Synthesis, Coordination Chemistry, and Properties of Indigo Diimines as a New Class of Functional Bridging Ligands. Chem. Commun. 2010, 46, 6753−6755. (e) Fortier, S.; Moral, O. G. -D.; Chen, C.-H.; Pink, M.; Le Roy, J. J.; Murugesu, M.; Mindiola, D. J.; Caulton, K. G. Probing the Redox Non-innocence of Dinuclear, Three-Coordinate Co(II) Nindigo Complexes: not Simply β-diketiminate Variants. Chem. Commun. 2012, 48, 11082−11084. (11) (a) Mondal, P.; Chatterjee, M.; Paretzki, A.; Beyer, K.; Kaim, W.; Lahiri, G. K. Noninnocence of Indigo: Dehydroindigo Anions as Bridging Electron-Donor Ligands in Diruthenium Complexes. Inorg. Chem. 2016, 55, 3105−3116. (b) Beck, W.; Schmidt, C.; Wienold, R.; Steimann, M.; Wagner, B. Indigo-Metal Complexes: Synthesis and Structure of PdII and PtII Compounds Containing the Anions of Indigo and Octahydroindigo as Mono- and Bis-Chelate Ligands. Angew. Chem., Int. Ed. Engl. 1989, 28, 1529−1531. (c) Wu, J.-Y.; Chang, C.H.; Thanasekaran, P.; Tsai, C.-C.; Tseng, C.-W.; Lee, G.-H.; Peng, S.M.; Lu, K.-L. Unusual Face-to-Face π−π Stacking Interactions within an Indigo-pillared M3(tpt)-Based Triangular Metalloprism. Dalton Trans. 2008, 6110−6112. (12) (a) Mandal, A.; Schwederski, B.; Fiedler, J.; Kaim, W.; Lahiri, G. K. Evidence for Bidirectional Noninnocent Behavior of a Formazanate Ligand in Ruthenium Complexes. Inorg. Chem. 2015, 54, 8126−8135. (b) Chang, M.-C.; Otten, E. Synthesis and Ligand-based Reduction
Chemistry of Boron Difluoride Complexes with Redox-Active Formazanate Ligands. Chem. Commun. 2014, 50, 7431−7433. (c) Barbon, S. M.; Price, J. T.; Reinkeluers, P. A.; Gilroy, J. B. Substituent-Dependent Optical and Electrochemical Properties of Triarylformazanate Boron Difluoride Complexes. Inorg. Chem. 2014, 53, 10585−10593. (13) (a) Shaffer, D. W.; Ryken, S. A.; Zarkesh, R. A.; Heyduk, A. F. Redox Behavior of Rhodium 9,10-Phenanthrenediimine Complexes. Inorg. Chem. 2011, 50, 13−21. (b) Gilroy, J. B.; Ferguson, M. J.; McDonald, R.; Patrick, B. O.; Hicks, R. G. Formazans as βdiketiminate Analogues. Structural Characterization of Boratatetrazines and Their Reduction to Borataverdazyl Radical Anions. Chem. Commun. 2007, 126−128. (c) Khusniyarov, M. M.; Bill, E.; Weyhermuller, T.; Bothe, E.; Wieghardt, K. Hidden Noninnocence: Theoretical and Experimental Evidence for Redox Activity of a βDiketiminate(1-) Ligand. Angew. Chem., Int. Ed. 2011, 50, 1652−1655. (14) (a) Tomson, N. C.; Labios, L. A.; Weyhermuller, T.; Figueroa, J. S.; Wieghardt, K. Redox Noninnocence of Nitrosoarene Ligands in Transition Metal Complexes. Inorg. Chem. 2011, 50, 5763−5766. (b) Barnett, B. R.; Labios, L. A.; Moore, C. E.; England, J.; Rheingold, A. L.; Wieghardt, K.; Figueroa, J. S. Solution Dynamics of Redox Noninnocent Nitrosoarene Ligands: Mapping the Electronic Criteria for the Formation of Persistent Metal-Coordinated Nitroxide Radicals. Inorg. Chem. 2015, 54, 7110−7121. (c) Kundu, S.; Stieber, C. E.; Ferrier, M. G.; Kozimor, S. A.; Bertke, J. A.; Warren, T. H. Redox Non-Innocence of Nitrosobenzene at Nickel. Angew. Chem., Int. Ed. 2016, 55, 10321−10325. (d) Chan, S.-C.; England, J.; Lee, W.-C.; Wieghardt, K.; Wong, C.-Y. Noninnocent Behavior of Nitrosoarene− Pyridine Hybrid Ligands: Ruthenium Complexes Bearing a 2 (2Nitrosoaryl)Pyridine Monoanion Radical. ChemPlusChem 2013, 78, 214−217. (15) Remenyi, C.; Kaupp, M. Where Is the Spin? Understanding Electronic Structure and g-Tensors for Ruthenium Complexes with Redox-Active Quinonoid Ligands. J. Am. Chem. Soc. 2005, 127, 11399−11413. (16) (a) Wang, P. G.; Xian, M.; Tang, X.; Wu, X.; Wen, Z.; Cai, T.; Janczuk, A. J. Nitric Oxide Donors: Chemical Activities and Biological Applications. Chem. Rev. 2002, 102, 1091−1134. (b) Jovene, C.; Chugunova, E. A.; Goumont, R. The Properties and the Use of Substituted Benzofuroxans in Pharmaceutical and Medicinal Chemistry: A Comprehensive Review. Mini-Rev. Med. Chem. 2013, 13, 1089−1136. (17) Chan, S.-C.; England, J.; Wieghardt, K.; Wong, C.-Y. Trapping of the Putative 1,2-Dinitrosoarene Intermediate of Benzofuroxan Tautomerization by Coordination at Ruthenium and Exploration of its Redox Non-innocence. Chem. Sci. 2014, 5, 3883−3887. (18) Patra, S.; Sarkar, B.; Maji, S.; Fiedler, J.; Urbanos, F. A.; JimenezAparicio, R.; Kaim, W.; Lahiri, G. K. Controlling Metal−Ligand−Metal Oxidation State Combinations by Ancillary Ligand (L) Variation in the Redox Systems [L2Ru(μ−boptz)RuL2]n, boptz = 3,6-bis(2-oxidophenyl)-1,2,4,5-tetrazine, and L = acetylacetonate, 2,2′- bipyridine, or 2phenylazopyridine. Chem. - Eur. J. 2006, 12, 489−498. (19) Velders, A. H.; van der Schilden, K.; Hotze, A. C. G.; Reedijk, J.; Kooijman, H.; Spek, A. L. Dichlorobis(2-phenylazopyridine)ruthenium(II) Complexes: Characterisation, Spectroscopic and Structural Properties of four Isomers. Dalton Trans. 2004, 448−455. (20) (a) Ghumaan, S.; Mukherjee, S.; Kar, S.; Roy, D.; Mobin, S. M.; Sunoj, R. B.; Lahiri, G. K. An Experimental and Density Functional Theory Approach Towards the Establishment of Preferential Metal- or Ligand-Based Electron-Transfer Processes in Large QuinonoidBridged Diruthenium Complexes [{(aap)2Ru}2(μ-BL2−)]n+ (aap = 2Arylazopyridine). Eur. J. Inorg. Chem. 2006, 2006, 4426−4441. (b) Das, A.; Scherer, T. M.; Mondal, P.; Mobin, S. M.; Kaim, W.; Lahiri, G. K. Experimental and DFT Evidence for the Fractional NonInnocence of a β-Diketonate Ligand. Chem. - Eur. J. 2012, 18, 14434− 14443. (21) El-Nahhal, I. M.; Heaton, G. S. Metal Complexes of some 2Nitrosoanilides. Inorg. Chim. Acta 1994, 223, 71−75. K
DOI: 10.1021/acs.inorgchem.6b02197 Inorg. Chem. XXXX, XXX, XXX−XXX
Article
Inorganic Chemistry (22) Arikawa, Y.; Yamaguchi, S.; Otsubo, Y.; Onishi, M.; Umakoshi, K. Ortho-Nitrosation of Anilines on a Ruthenium Hydridotris(pyrazolyl)borato Complex and Oxidation of the Resulting Coordinated Amine Groups. Organometallics 2015, 34, 1056−1061. (23) Santra, B. K.; Thakur, G. A.; Ghosh, P.; Pramanik, A.; Lahiri, G. K. A Novel Example of Metal-Mediated Aromatic Thiolation in a Ruthenium Complex. Crystal Structure of RuII(SC6H4NNC6H4N)2. Inorg. Chem. 1996, 35, 3050−3052. (24) Popov, A. M.; Egorova, M. B.; Lutovinov, V. A.; Dmitrieva, R. I. Directed Synthesis of an Unknown Isomer of a Bis Chelate Complex of Ruthenium(II) with a-(Phenylazo)Pyridine. Zh. Obshch Khim. 1990, 60, 2169−2170. (25) Mandal, A.; Grupp, A.; Schwederski, B.; Kaim, W.; Lahiri, G. K. Noninnocently Behaving Bridging Anions of the Widely Distributed Antioxidant Ellagic Acid in Diruthenium Complexes. Inorg. Chem. 2015, 54, 10049−10057. (26) Majumdar, P.; Peng, S.-M.; Goswami, S. Biimidazole complexes of ML2 2+ [M = Ru or Os, L = 2-(phenylazo)- pyridine]. Synthesis, Structure and Redox Properties of Mono- and di-nuclear Complexes. J. Chem. Soc., Dalton Trans. 1998, 1569−1574. (27) Gerson, F.; Huber, W. Electron Spin Resonance of Organic Radicals; Wiley-VCH: Weinheim, Germany, 2003. (28) Creutz, C. Mixed valence complexes of d5-d6 metal centers. Prog. Inorg. Chem. 1983, 30, 1−73. (29) Patra, S.; Sarkar, B.; Mobin, S. M.; Kaim, W.; Lahiri, G. K. Separating Innocence and Non-Innocence of Ligands and Metals in Complexes [(L)Ru(acac)2]n (n = − 1, 0, + 1; L = o-Iminoquinone or o-Iminothioquinone). Inorg. Chem. 2003, 42, 6469−6473. (30) (a) Ozarowski, A.; McGarvey, B. R.; Peppe, C.; Tuck, D. G. Metal(II) Derivatives of 3,5-Di-tert-butyl-1,2-o-benzoquinone. EPR Study of Conformation in Biradicals. J. Am. Chem. Soc. 1991, 113, 3288−3293. (b) Das, D.; Mondal, T. K.; Chowdhury, A. D.; Weisser, F.; Schweinfurth, D.; Sarkar, B.; Mobin, S. M.; Urbanos, F. A.; Jimenez-Aparicio, R.; Lahiri, G. K. Valence and Spin Situations in Isomeric [(bpy)Ru(Q′)2]n (Q′ = 3,5-di-tert-butyl-N-Aryl-1,2-Benzoquinonemonoimine). An Experimental and DFT Analysis. Dalton Trans. 2011, 40, 8377−8390. (31) (a) Kaim, W.; Ernst, S.; Kasack, V. ESR of Homo- and Heteroleptic Mono- and Dinuclear Tris(α-diimine)ruthenium Radical Complexes. J. Am. Chem. Soc. 1990, 112, 173−178. (b) Heilmann, M.; Baumann, F.; Kaim, W.; Fiedler, J. Configuration-dependent Electron Hopping between Equivalent Ligands in Isomeric Ruthenium(II) Complexes. J. Chem. Soc., Faraday Trans. 1996, 92, 4227−4231. (32) Miller, J.; Min, K. S. Oxidation Leading to Reduction: RedoxInduced Electron Transfer (RIET). Angew. Chem. 2009, 121, 268− 278; Angew. Chem., Int. Ed. 2009, 48, 262−272. (33) (a) Mondal, P.; Agarwala, H.; Jana, R. D.; Plebst, S.; Grupp, A.; Ehret, F.; Mobin, S. M.; Kaim, W.; Lahiri, G. K. Sensitivity of a Strained C−C Single Bond to Charge Transfer: Redox Activity in Mononuclear and Dinuclear Ruthenium Complexes of Bis(arylimino)acenaphthene (BIAN) Ligands. Inorg. Chem. 2014, 53, 7389−7403. (b) Das, D.; Agarwala, H.; Chowdhury, A. D.; Patra, T.; Mobin, S. M.; Sarkar, B.; Kaim, W.; Lahiri, G. K. Four-Center Oxidation State Combinations and Near-Infrared Absorption in [Ru (pap)(Q)2]n (Q = 3,5-Di-tert butyl-N-aryl-1,2-benzoquinonemonoimine, pap = 2 Phenylazopyridine). Chem. - Eur. J. 2013, 19, 7384−7394. (34) Krause, R. A.; Krause, K. Chemistry of Bipyridyl-like Ligands. Isomeric Complexes of Ruthenium(I1) with 2- (Phenylazo) pyridine. Inorg. Chem. 1980, 19, 2600−2603. (35) (a) Sheldrick, G. M. A short history of SHELX. Acta Crystallogr., Sect. A: Found. Crystallogr. 2008, A64, 112−122. (b) Program for Crystal Structure Solution and Refinement; University of Goettingen: Goettingen, Germany, 1997. (c) Sheldrick, G. M. Crystal structure refinement with SHELXL. Acta Crystallogr., Sect. C: Struct. Chem. 2015, C71, 3−8. (36) van der Sluis, P.; Spek, A. L. BYPASS: an effective method for the refinement of crystal structures containing disordered solvent regions Acta Crystallogr. Acta Crystallogr., Sect. A: Found. Crystallogr. 1990, A46, 194−201.
(37) Lee, C.; Yang, W.; Parr, R. G. Development of the Colic-Salvetti Correlation-Energy Formula into a Functional of the Electron Density. Phys. Rev. B: Condens. Matter Mater. Phys. 1988, 37, 785−789. (38) (a) Andrae, D.; Haeussermann, U.; Dolg, M.; Stoll, H.; Preuss, H. Energy-adjusted ab intio Pseudopotentials for the Second and Third Row Trasition Elements. Theor. Chim. Acta 1990, 77, 123−141. (b) Fuentealba, P.; Preuss, H.; Stoll, H.; von Szentpaly, L. A Proper Account of Core-Polerizantion with Pseudopotentials: Single ValanceElectron Alkali Compounds. Chem. Phys. Lett. 1982, 89, 418−422. (39) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, O.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian 09, Revision A.02; Gaussian, Inc: Wallingford, CT, 2009. (40) (a) Bauernschmitt, R.; Ahlrichs, R. Treatment of Electronic Excitations within the Adiabatic Approximation of Time Dependent Density Functional Theory. Chem. Phys. Lett. 1996, 256, 454−464. (b) Stratmann, R. E.; Scuseria, G. E.; Frisch, M. J. An Efficient Implementation of Time-Dependent Density-Functional Theory for the Calculation of Excitation Energies of Large Molecules. J. Chem. Phys. 1998, 109, 8218−8225. (c) Casida, M. E.; Jamorski, C.; Casida, K. C.; Salahub, D. R. Molecular Excitation Energies to High-Lying Bound States from Time-Dependent Density Functional Response Theory: Characterization and Correction of the Time-Dependent Local Density Approximation Ionization Threshold. J. Chem. Phys. 1998, 108, 4439−4450. (41) (a) Barone, V.; Cossi, M. Quantum Calculation of Molecular Energies and Energy Gradients in Solution by a Conductor Solvent Model. J. Phys. Chem. A 1998, 102, 1995−2001. (b) Cossi, M.; Barone, V. Time-dependent density functional theory for molecules in liquid solutions. J. Chem. Phys. 2001, 115, 4708−4718. (c) Cossi, M.; Rega, N.; Scalmani, G.; Barone, V. Energies, Structures, and Electronic Properties of Molecules in Solution with the C-PCM Solvation Model. J. Comput. Chem. 2003, 24, 669−681. (42) Leonid, S. Chemissian 1.7; 2010. Available at http://www. chemissian.com. (43) Zhurko, G. A.; Zhurko, D. A. ChemCraft 1.6; Plimus: San Diego, CA. Online: http://www.chemcraftprog.com. (44) Gorelsky, S. I. SWizard program. http://www.sg-chem.net/. (45) Gorelsky, S. I.; Lever, A. B. P. Electronic Structure and Spectra of Ruthenium Diimine Complexes by Density Functional Theory and INDO/S. Comparison of the Two Methods. J. Organomet. Chem. 2001, 635, 187−196. (46) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865−3868.
L
DOI: 10.1021/acs.inorgchem.6b02197 Inorg. Chem. XXXX, XXX, XXX−XXX
