Rhenium(I) Tricarbonyl Complexes of meso-Tetraaryl-21,23

Article pubs.acs.org/IC

Rhenium(I) Tricarbonyl Complexes of meso-Tetraaryl-21,23diheteroporphyrins Tejinder Kaur, Way-Zen Lee, and Mangalampalli Ravikanth* Department of Chemistry, Indian Institute of Technology, Bombay, Powai, Mumbai 400 076, India Instrumentation Center, Department of Chemistry, National Taiwan Normal University, 88 Section, 4 Ting-Chow Road, Taipei 11677, Taiwan S Supporting Information *

ABSTRACT: The dithia/diselena meso-tetraarylporphyrins have a lesser tendency to form metal complexes because of the larger size of the heteroatom(s), which shrinks the cavity size, and the heteroatoms also have poor coordinating ability to bind metal ions. The first example of a rhenium(I) tricarbonyl complex of 21,23diselenaporphyrin was synthesized by treating 5,10,15,20-tetra-ptolyl-21,23-diselenaporphyrin with Re(CO)5Cl in chlorobenzene at reflux temperature and its structural properties were compared with our earlier reported rhenium(I) complex of tetraaryl-21,23dithiaporphyrin. The crystal structures of rhenium(I) complexes of diheteroporphyrins revealed that the ReI ion binds to both the Se/S atoms and one of the N atoms of the porphyrin core along with three terminal carbonyl groups in an octahedral fashion. The rhenium(I) complexes of 21,23-diheteroporphyrins are stabilized by a large counterion, the trichloro-bridged dirhenium(I) ion. We also present a detailed account of the spectral and redox properties of rhenium(I) tricarbonyl complexes of 21,23diheteroporphyrins.

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dithiaporphyrin16,17 resulting from the replacement of two pyrrole rings by thiophene rings, and two metal complexes of 21-selenaporphyrin18,19 resulting from the replacement of one pyrrole ring by selenophene, and to the best of our knowledge, there is no metal complex reported for 21,23-diselenaporphyrin resulting from the replacement of two pyrrole rings by selenophene rings. In 1999, Hung and co-workers prepared the first example of a metallodithiaporphyrin, the ruthenium(II) complex S2TTP, and showed that 21,23-dithiaporphyrins also form metal complexes. In a recent communication,17 we reported the synthesis and structure of a stable rhenium(I) complex of 21,23-dithiaporphyrin, a second example of a metallodithiaporphyrin, under simple reaction conditions. Our investigation revealed that Re(CO)3 binds with two thiophene S atoms and one of the pyrrole N atoms in 21,23dithiaporphyrin to form a stable six-coordinated rhenium(I) complex. This success encouraged us to prepare the first example of the Re(CO)3 complex of 21,23-diselenaporphyrin. Thus, herein, we report a detailed account of the synthesis, structure, and properties of the second example of a rhenium(I) tricarbonyl complex of 5,10,15,20-tetra-p-tolyl-21,23-dithiaporphyrin (1; S2TTP) and the first example of a rhenium(I) tricarbonyl complex of 5,10,15,20-tetra-p-tolyl-21,23-diselenaporphyrin (2; Se2TTP) and compare the properties with an

INTRODUCTION Core-modified porphyrins or heteroporphyrins resulting from the replacement of one or two pyrrole N atoms with heteroatoms such as C, S, Se, Te, P, and Si exhibit interesting and different physicochemical properties compared to regular porphyrins.1 One of the interesting features of heteroporphyrins is their metal coordination chemistry. Porphyrins have two ionizable protons and are known to bind almost all of the metals in the periodic table. This metal incorporation may result in distortion of the planar macrocycle in order to maximize the binding strength toward the metal fragment.2 However, when the pyrrole N atom is substituted with heteroatoms such as S and Se, the resulting heteroporphyrins possess a poor ability to bind metal ions, which can be attributed to a decrease of the porphyrin core size, a reduction in the number of ionizable protons, and also structural deformation of the porphyrin ring, to name a few.3 However, a perusal of the literature reveals that the heteroporphyrins stabilize metals in unusual oxidation states such as Cu and Ni in the 1+ oxidation state, which is not easy to obtain with regular porphyrins. Furthermore, the coordination chemistry of heteroporphyrins is not extensively developed like regular porphyrins because of the above-mentioned constraints, and it remained a challenging task to prepare metal complexes of heteroporphyrins. In the literature, there are only nine metal complexes of 21-monothiaporphyrins4−15 resulting from the replacement of NH by S atom, two metal complexes of 21,23© XXXX American Chemical Society

Received: February 3, 2016

A

DOI: 10.1021/acs.inorgchem.6b00214 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry Chart 1. Structures of Complexes 3−5

Scheme 1. Synthesis of Complexes 1 and 2

earlier reported ruthenium(II) complex of S2TPP (3; see Chart 1), a Re(CO)3 complex of 21-thiaporphyrin (4), and a Re(CO)3 complex of 21-selenaporphyrin (5). The studies revealed that ReI is stabilized inside a N2X2 porphyrin core by a large counteranion, the trichloro-bridged dirhenium(I), and the porphyrin macrocycle is severely distorted to accommodate the ReI ion compared to the corresponding free-base N2X2 porphyrin.

Table 1. Crystallographic Data for Compounds 1 and 2 parameter CCDC mol formula fw cryst syst space group a (Å) b (Å) c (Å) α (deg) β (deg) γ (deg) V (Å3) Z μ (mm−1) Dcalcd F(000) θ range (deg) indep reflns

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RESULTS AND DISCUSSION The Re(CO)3 complexes of S2TTP and Se2TTP were prepared by treating the appropriate porphyrin with 1.1 equiv of Re(CO)5Cl in chlorobenzene at reflux temperature for 8 h (Scheme 1). Progress of the reaction was monitored by thinlayer chromatography (TLC) and UV−vis spectra. As the reaction progressed, TLC analysis showed the appearance of a more polar green spot and the disappearance of the spot corresponding to the starting free-base porphyrin. The absorption spectra also indicated the possibility of the formation of Re(CO)3 complexes of N2X2 porphyrins. The crude solid was filtered, washed several times with a mixture of dichloromethane/petroleum ether, and recrystallized from dichloromethane/petroleum ether to afford complexes 1 and 2 as green crystals in 74% and 78% yield, respectively. Highresolution mass spectrometry (HRMS), IR and NMR spectroscopies, and X-ray crystallographic techniques also confirmed the formation of complexes 1 and 2. Crystallographic Characterization. The structures of complexes 1 and 2 were determined by single-crystal X-ray crystallography. Complexes 1 and 2 were crystallized via the slow diffusion of n-pentane into dichloromethane over a period of 2 days. Crystal data and data collection parameters are summarized in Table 1, and selected crystal structure parameters for complexes 1 and 2 are presented in Table 2. Both of the complexes have a number of common features. Both 1 and 2 were found to be crystallized in the triclinic space group P1̅ and adopt nearly saddle-shaped structures. To gain more insight into the binding mode of the ReI ion and to understand its effect on the macrocyclic distortion, we compared the structures of complexes 1 and 2 with that of the reported analogous six-coordinated ruthenium(II) complex of S2TTP (3)16 as well as the Re(CO)3 complex of 5,10,15,20-

R1, wR2 [I > 2σ(I)] R1, wR2 (all data) GOF largest diff peak, hole (e Å−3)

1

2

972267 C57 H36 Cl3 N2 O9 Re3 S2 1621.95 triclinic P1̅ 14.69(2) 14.759(15) 15.618(13) 61.23(9) 63.80(7) 80.86(11) 2657(5) 2 7.106 2.027 g cm−3 1544 2.13−25.00 9268 [R(int) = 0.0966] 0.0910, 0.2464 0.0951, 0.2517 1.085 3.333, −6.369

1436568 C57H36C13N2O9Re3Se2 1715.75 triclinic P1̅ 14.754(12) 14.763(12) 15.556(10) 64.15(3) 61.78(2) 81.56(2) 2679(3) 2 8.327 2.127 Mg m−3 1616 1.64−25.19 9463 [R(int) = 0.1051] 0.0753, 0.1595 0.1676, 0.1969 1.007 3.148, −2.229

tetraphenyl-21-thiaporphyrin (4)15 and the Re(CO)3 complex of 5,10,15,20-tetraphenyl-21-selenaporphyrin (5).19 Unlike the neutral ruthenium(II) complex of 3, complexes 1 and 2 are ionic and consist of cationic [Re(CO)3N2S2TTP]+ with a trichloro-bridged dirhenium(I) ion, [Re2(μ-Cl)3(CO)6]−, as the counterion. As shown in Figure 1, in both complexes 1 and 2, the ReI ion was coordinated to one of the N atoms, two heteroatoms (S/ Se) present in the core of the macrocycle, and three axial carbonyl groups in an octahedral fashion. However, in 3, the octahedral geometry of the RuII ion was satisfied by coordinating to all of the four-coordinated atoms, two S and two N atoms, of the porphyrin core and two axial chloro ligands in a trans fashion. In complexes 1 and 2, the ReI ion B

DOI: 10.1021/acs.inorgchem.6b00214 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry

was displaced to a larger extent compared to complexes 4 and 5 (∼1.52 Å). In complexes 1 and 2, the two thiophene S atoms/ selenophene Se atoms bent downward and one pyrrole N atom bent upward to coordinate with the ReI ion in such a way that the ReI ion is equidistant from the coordinating heteroatoms and the coordinated pyrrole N atom is placed at a shorter distance compared to the heteroatoms (Figure 1). The noncoordinated N atom bent away from the ReI ion. In 3, both of the S atoms bent in the opposite direction to the same extent (0.925 Å) and the N atoms remained almost in the same plane (0.024 Å) to coordinate with the RuII ion. It is also observed in complex 1 that the coordinated atoms S1, S2, and N2 deviate significantly (0.209, 0.254, and 0.307 Å, respectively) compared to the noncoordinated pyrrole N1 atom (0.165 Å) from the mean plane comprised of 24 pophyrin core atoms. In complex 2, further notable deviations were observed for coordinated atoms Se1, Se2, and N2 (0.388, 0.320, and 0.321 Å, respectively) from the mean plane compared to the noncoordinated N1 atom (0.180 Å). These deviations indicate that complexes 1 and 2 are more distorted in nature compared to 3 (Table 2). Furthermore, we compared the outof-plane displacements in units of 0.01 Å of the core atoms of complexes 1 and 2, as presented in parts c and d of Figure 1, respectively. The coordinated heterorings deviated significantly from the least-squares plane of the dithia/selenaporphyrin core atoms and arranged in an alternating up and down manner similar to the saddled deformations observed in some porphyrin macrocycles.20 The noncoordinated pyrrole underwent minimal deviation and remained almost in the leastsquares plane of the dithia/selenaporphyrin core atoms. Furthermore, the Re−N2 and Re−S/Se distances (2.24 and 2.54 Å, respectively) were significantly longer in complexes 1 and 2 compared to complex 3 but were comparable with those of complexes 4 and 5. However, the Re−N1 distances in 1 and 2 (3.45 and 3.51 Å) were much longer than those observed for 4 (3.24 Å) and 5 (3.32 Å). The Se1−Se2 distance in 2 was much shorter (3.02 Å) than the S1−S2 distance (3.15 Å) in 1. In complex 3, the S1−S2 distance was much longer (4.50 Å) than that in complex 1. In both complexes 1 and 2, the anion consists of two Re ions bridged by three Cl atoms and the octahedral coordination at each ReI ion is completed by three terminal carbonyl groups. The average Re−Cl distance is ∼2.51 Å, and the average Re−C distance of the Re−CO unit is ∼1.86 Å, which is shorter than the Re−C distance of the Re−CO unit (1.93 Å) of the cationic moiety. The average angle of the Re−Cl−Re bonds is ∼84.40°, and the Re−Re distance is 3.380 Å in 1 and 3.356 Å in 2, which are too long to postulate a direct metal−metal interaction. These bond lengths and angles of the anionic moiety of complexes 1 and 2 were almost in the same range as those observed for such rhenium(I) complexes.21 Thus, the crystal structure revealed that complexes 1 and 2 are significantly distorted compared to the corresponding free-base porphyrin N2X2 and stabilized as the cationic moiety with the trichlorobridged dirhenium complex as the counteranionic moiety. NMR Studies. Complexes 1 and 2 were further characterized by detailed NMR studies. A comparison of the 1 H NMR spectra of complexes 1 and 2 along with their freebase porphyrins S2TTP and Se2TTP is presented in Figure 2. In the 1H NMR spectrum of S2TTP 1, the four thiophene protons appeared as one singlet at 9.69 ppm, the four pyrrole protons appeared as one singlet at 8.69 ppm, and the 16 meso-aryl protons appeared as two sets of doublets at 8.14 and 7.62 ppm.

Table 2. Some Selected Crystal Structure Parameters for Complexes 1−5 parameter

1

2

3

4

5

Δ24Re/Ru a Δ24S1/Se1 b Δ24S2/Se2/N3 c Δ24N1 d Δ24N2 e Δ 3Re /Δ 4Ru f l

1.676 0.209 0.254 0.165 0.307 1.729 1.944 1.952 1.930 1.121 1.079 1.072 1.750 1.400

1.669 0.388 0.320 0.180 0.321 1.774 1.894 1.902 1.901 1.131 1.146 1.159 1.891 1.401

0.000 0.925 0.925 0.024 0.024 0.000

1.666 0.159 0.118 0.401 0.245 1.448 1.898 1.907 1.885 1.166 1.158 1.158 1.770 1.431

1.571 0.412 1.523 1.909 1.916 1.912 1.134 1.153 1.164 1.932 1.404

Re−CO

ReC−Ol

S/Se−Cα Cα−Cβ

1.750 1.390

a

Displacement (in Å) of Re/Ru from the 24-atom mean plane of the porphyrin core. bDisplacement (in Å) of a heteroatom (X = S/Se/O) from the 24-atom mean plane of the porphyrin core. cDisplacement (in Å) of N1 from the 24-atom mean plane of the porphyrin core. d Displacement (in Å) of N2 from the 24-atom mean plane of the porphyrin core. eDisplacement (in Å) of N3 from the 24-atom mean plane of the porphyrin core. fDisplacement (in Å) of Re/Ru from the mean plane of three/four-coordinated atoms of the porphyrin core.

Figure 1. Single-crystal X-ray structure of complexes 1 and 2: (a and b) perspective view; (c and d) diagram showing out-of-plane displacements (in units of 0.01 Å) of the core atoms of complexes 1 and 2 from the mean plane consisting of C20N2Se2Re atoms; (e and f) simplified geometrical representation of complexes 1 and 2 showing the coordination features around the central ReI ion.

being the 5d transition-metal ion and larger in size is placed at ∼1.73 Å above the three-coordinated atoms of the porphyrin, unlike in complex 3, where the RuII ion is almost in the plane of the macrocycle. Furthermore, the ReI ion in complexes 1 and 2 C

DOI: 10.1021/acs.inorgchem.6b00214 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry

Figure 2. Comparison of the 1H NMR spectra of compounds 1 and 2 with the corresponding free-base porphyrins S2TTP and Se2TTP recorded in CDCl3 at room temperature.

Figure 3. Variable-temperature 1H NMR spectra of complex 2 recorded in CDCl3.

selenophene protons are a direct indication that the heteroatoms S/Se in the corresponding N2X2 heteroporphyrins are involved in bonding with the ReI ion. In both of these complexes 1 and 2, we noted two singlets for four pyrrole protons, indicating that only one pyrrole is involved in coordination with the ReI ion and the other pyrrole remains uncoordinated. Although we expect the possibility of fluxionality in such complexes, the NMR spectral study supported the existence of the same structure in the solution, as observed in their solid state, and ruled out the possibility of such fluxional behavior of these complexes. We carried out further variable-temperature NMR studies as well as protonation studies on complexes 1 and 2, as shown in Figures 3 and 4. Both variable-temperature and protonation studies showed negligible downfield shifts for β-pyrrole protons, indicating the absence of fluxional behavior in complexes 1 and 2. However, under these conditions, the broad meso-aryl resonances were sharpened and well resolved. At room temperature, the meso-

In complex 1, the four thiophene protons were significantly downfield-shifted and appeared as two doublets at 10.40 and 10.33 ppm; the four pyrrole protons appeared as two singlets at 8.71 and 8.59 ppm, and the meso-aryl protons appeared as five sets of broad resonances in the 8.47−7.67 ppm region. The meso-tolyl-CH3 protons also appeared as two singlets at 2.79 and 2.76 ppm, reflecting the unsymmetric nature of complex 1. Similarly, the free-base Se2TTP shows one singlet at 9.86 ppm for four selenophene protons, one singlet at 8.80 ppm for four pyrrole protons, two sets of aryl signals at 8.15 and 7.65 ppm, and one singlet at 2.72 ppm for 12 meso-tolyl-CH3 protons. In complex 2, the four selenophene protons were significantly downfield-shifted and appeared as two doublets at 10.39 and 10.36 ppm; the four pyrrole protons appeared as two singlets at 8.84 and 8.65 ppm, and the meso-aryl protons appeared as broad resonances in the 8.70−7.56 ppm region. The meso-tolylCH3 protons also appeared as two singlets at 2.80 and 2.75 ppm . Significant downfield shifts in the β-thiophene and βD

DOI: 10.1021/acs.inorgchem.6b00214 Inorg. Chem. XXXX, XXX, XXX−XXX

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Figure 4. 1H NMR titration of complex 2 with increasing addition of TFA in CDCl3 recorded at room temperature.

Table 3. Absorption and Redox Data of All of the Compounds absorption and emission data λ, nm (log ε, M−1 cm−1)

a

redox datab

compound

Soret bands

Q bands

λem, nm

S2TTP 1 1·H+ Se2TTP 2 2·H+

436 (5.48) 438, 453(sh) (4.96) 466 448 (5.16) 454 (br) (4.76) 465

515 (4.44), 548 (3.98), 632 (3.11), 698 (3.77) 515, 545 (4.09), 595 (3.99), 700 (3.50), 792 (3.89) 533, 710, 787 527 (4.32), 566 (3.68), 632 (3.40), 695 (3.59) 541 (4.11), 620 (3.90), 816 (3.83) 555, 611, 746, 808

711 728

1.18 1.65

−0.94, −1.21 −0.09, −0.50, −0.92, −1.29

874 896

1.14 0.15, 1.74

−0.88, −1.18 −0.25, −0.61, −0.72, −1.08

a

oxidation, V

reduction, V

λex = 450 nm. bHalf-wave potentials in CH2Cl2 with 0.1 M Bu4NClO4 vs SCE. Scan rate = 50 mV s−1.

Figure 5. (a) Comparison of the absorption plots of complexes 2 (red) and 2·H+ (blue) along with N2Se2TTP (black). The concentrations used were 10−5 M. (b) Comparison of the redox plots of complex 2 (bottom) and N2Se2TTP (top).

rotation of the meso-aryl groups was restricted, leading to sharp and well-resolved resonances of the meso-aryl protons. 13C NMR and IR spectroscopy confirmed the presence of CO groups in complexes 1 and 2. In the 13C NMR spectrum, the carbonyl groups showed two signals at 187.2 and 184.3 ppm for complex 1 and 188.0 and 188.18 ppm for complex 2, which is in line with the reported rhenium(I) complexes.15,17 In the IR

aryl protons were observed as broad resonances because of rotation of the meso-aryl groups because the tilting of the thiophene/selenophene ring out of the porphyrin plane reduces steric congestion at the periphery of the macrocycle and facilitates rotation of the meso-aryl groups, as observed by Eaton and co-workers22 for metal complexes of meso-tetraarylporphyrins. However, at low-temperature and protonation conditions, E

DOI: 10.1021/acs.inorgchem.6b00214 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry

bands along with one strong Soret band, and the complexes were stable under protonation and redox conditions.

spectrum of complex 1, six absorptions at 2041, 2019, 1940, 1928, 1904, and 1897 cm−1 were observed. The absorptions at 2019, 1904, and 1897 cm−1 can be attributed to the carbonyl groups of the cationic moiety because these absorptions are in line with complexes 4 and 5.15,19 The remaining three absorptions can be attributed to the carbonyl groups of the anionic moiety. In the case of complex 2, we observed absorptions at 2042 and 2020 cm−1 along with a broad absorption at 1905 cm−1 (see the Supporting Information). Absorption and Redox Studies. The absorption spectral properties of 1 and 2 along with their free-base porphyrins S2TTP and Se2TTP, respectively, were studied, and the data are presented in Table 3. A comparison of the absorption spectra of 2, protonated 2 (2·H+), and Se2TTP is shown in Figure 5. Complex 1 showed five broad ill-defined Q bands in the range of 500−800 nm along with one Soret band at 438 nm with a shoulder at 453 nm. Complex 2 also showed similar absorption features with one broad Soret band at 454 nm and ill-defined Q bands at 541, 620, and 816 nm. Upon the addition of an excess of trifluoroacetic acid (TFA) to a dichloromethane solution of complex 1, the resulting protonated compound 1·H+ showed one Soret band at 466 nm and three Q bands in the visible region at 533, 710, and 787 nm, which were red-shifted with a reduction in the extinction coefficients compared to their freebase porphyrins (Table 3). The protonated absorption spectrum of complex 2 (2·H+) also showed similar features with one Soret band at 465 nm and three Q bands in the visible region at 555, 611, and 808 nm (Figure 5a). Complexes 1 and 2 were weakly fluorescent (see the Supporting Information). The electrochemical properties of 1 and 2 were investigated by cyclic voltammetry using tetrabutylammonium perchlorate (TBAP) as the supporting electrolyte and a saturated calomel electrode (SCE) as the reference electrode in dichloromethane as the solvent. In general, S2TTP and Se2TTP showed one oxidation and two reductions, whereas complexes 1 and 2 showed two oxidations and four reductions (Figure 5b). The additional oxidation and two reductions were attributed to the anionic moiety based on the literature.20 For example, complex 2 showed two oxidations at 0.15 and 1.74 V and four reductions at −0.25, −0.61, −0.72, and −1.08 V. In this case, the oxidation at 1.74 V and two reductions at −0.72 and −1.08 V were due to the cationic rhenium(I) porphyrin, whereas the oxidation at 0.15 V and two reductions at −0.25 and −0.61 V were attributed to the anionic chloro-bridged dirhenium complex moiety. Complex 1 also showed similar redox behavior. More studies are required to understand the redox behavior of the rhenium(I) complexes 1 and 2.

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EXPERIMENTAL SECTION

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ASSOCIATED CONTENT

General Procedures. Tetrahydrofuran and dichloromethane were dried by standard procedures before use. 2,3-Dichloro-5,6-dicyano-1,4benzoquinone was obtained from Spectrochem (India). Column chromatography was performed on silica (60−120 mesh) or alumina. 1 H NMR spectra (δ in ppm) were recorded using a Bruker 500 MHz spectrometer in CDCl3. Absorption and fluorescence spectra were recorded at 25 °C in a 1 cm quartz fluorescence cuvette. Cyclic voltammetry studies were carried out with an electrochemical system utilizing the three-electrode configuration consisting of glassy carbon (working electrode), platinum wire (auxiliary electrode), and saturated calomel (reference electrode) electrodes. The experiments were done in dry dichloromethane using 0.1 M TBAP as the supporting electrolyte. All potentials were calibrated versus SCE by the addition of ferrocene as an internal standard, taking E1/2(Fc/Fc+) = 0.51 V, vs SCE. HRMS spectra were recorded in a Q-TOF micromass spectrometer based on the electrospray ionization method. Single crystals of suitable size for X-ray diffractometry were selected under a microscope and mounted on the tip of a glass fiber, which was positioned on a copper pin. The X-ray data for complex 2 were collected on a Bruker Kappa CCD diffractometer, employing graphitemonochromated Mo Kα radiation at 200 K and the θ−2θ scan mode. The structure of complex 2 was solved by direct methods using SIR92 or SIR9723 and refined with SHELXL-97.24 An empirical absorption correction by multiscans was applied. All non-H atoms were refined with anisotropic displacement factors. H atoms were placed in ideal positions and fixed with relative isotropic displacement parameters. Synthesis of Complex 2. To a solution of 5,10,15,20-tetra-p-tolyl21,23-Diselenaporphyrin (50 mg, 0.063 mmol)) in chlorobenzene was added Re(CO)5Cl (27 mg, 0.075 mmol), and the reaction mixture was refluxed for 8 h. The progress of the reaction was monitored by TLC and UV−vis absorption spectroscopy. The deep orange changed to brownish green. The complex was isolated as a brown solid after recrystallization from CH2Cl2/pentane. Yield: 78% (52 mg, 0.049 mmol). 1H NMR (400 MHz, CDCl3): δ 10.39 (d, J(H,H) = 5.10 Hz, 2H, β-thiophene H), 10.36 (d, J(H,H) = 5.15 Hz, 2H, β-thiophene H), 8.84 (s, 2H, β-pyrrole H), 8.65 (s, 2H, β-pyrrole H), 8.70−7.56 (broad resonances, Ar), 2.80 (s, 6H, −CH3), 2.75 (s, 6H, −CH3). 13C NMR (500 MHz CDCl3): δ 188.0, 188.2, 162.8, 161.0, 149.5, 145.8, 142.7, 141.9, 140.4, 139.4, 139.2, 137.5, 136.6, 136.3, 135.4, 134.5, 134.2, 133.7, 130.3, 129.9, 129.6, 129.4, 128.8, 21.9, 21.8. HRMS (ESI). Calcd for C51H37N2O3ReSe2: m/z 1072.0855 [(M + H)+]. Found: m/z 1072.0852 [(M + H)+].

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.6b00214. Experimental, spectral, and crystallographic data of complex 2 (PDF) X-ray crystallographic data in CIF format (CIF)

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CONCLUSIONS In conclusion, we synthesized rhenium(I) complexes of dithiaand diselenaporphyrin by reacting S2TTP/Se2TTP with Re(CO)5Cl in chlorobenzene at reflux temperature. The complexes were isolated in pure form by simple recrystallization. These are rare examples of metal complexes of N2X2 porphyrins, which are known to show poor coordination ability to form metal complexes. The crystal structures revealed that, in complexes 1 and 2, the porphyrin ring was significantly distorted and the ReI ion was placed above the porphyrin ring. The ReI ion was coordinated to one of the pyrrolic N atoms, two heteroatoms of the porphyrin core, and three carbonyl groups to form ionic octahedral complexes 1 and 2. The absorption studies of complexes 1 and 2 showed ill-defined Q

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We thank the Department of Science and Technology, India, and IRCC IIT Bombay for financial support. F

DOI: 10.1021/acs.inorgchem.6b00214 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry

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REFERENCES

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DOI: 10.1021/acs.inorgchem.6b00214 Inorg. Chem. XXXX, XXX, XXX−XXX