Role reversal of carboxylate group from coordination to H-bonding

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Role reversal of carboxylate group from coordination to H-bonding only, in structurally diverse metal-2-amino, 5-nitro-benzoates- A first report. Amanpreet Kaur Jassal, Balkaran Singh Sran, Kalyanashis Mandal, Pritam Mukhopadhyay, and Geeta Hundal Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.8b00771 • Publication Date (Web): 10 Jul 2018 Downloaded from http://pubs.acs.org on July 12, 2018

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Crystal Growth & Design

Role reversal of carboxylate group from coordination to H-bonding only, in structurally diverse metal-2-amino, 5-nitro-benzoates- A first report.

Amanpreet Kaur Jassal, † Balkaran Singh Sran, † Kalyanashis Mandal, ‡ Pritam Mukhopadhyay, ‡* Geeta Hundal * † † Department of Chemistry, UGC sponsored centre of advance studies-II,

Guru Nanak Dev University, Amritsar-143005, Punjab, India ‡ Supramolecular and Material Chemistry Lab, School of Physical

Sciences, Jawaharlal Nehru University, New Delhi-110067, India [email protected] , [email protected]

Abstract- The remarkable structural diversities arising from a small ligand, 2-amino,5-nitro-benzoic acid (L1H), equipped with different functional groups, conferring tunable coordination sites as well as H-bonding abilities, have been explored. Six new crystal structures of Cs(I), Na(I), K(I) and Li(I) ions with L1 have been realized. Notably, for the medium sized alkali metal ions a role reversal between the coordination and H-bonding nature of –COO- and –NO2 groups, respectively, has been observed for the first time. Since L1 possesses three potential sites for coordination as well as H-bonding interactions, we realized a delicate control of non-covalent interactions on the resulting supramolecular assemblies. Structural diversities observed range from 1D helices and linear threads to 2D brickwall types or 3D networks. Electrostatic surface potential (ESP) of three representative complexes provided an insight into the electronic deficient and electron rich regions. The coordination of Na(I) and K(I) ions through the nitro groups extends the electron deficient region of the complexes. The electron densities at the bond critical paths (BCPs) of the representative complexes were calculated to understand the supramolecular outcome of the coordination polymers. Unravelling of such critical electronic information is paramount towards the systematic construction of new generation of complex coordination polymers (CPs).

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Crystal Growth & Design 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Introduction The glue for the inorganic “crystal engineering” is metal-ligand coordinate-covalent bond whose strength and directionality

has been thoroughly exploited for

engineering various molecular building blocks into diverse supramolecular architectures.1 It is well known that the dimensionality of the resulting coordination networks can be increased by non-covalent interactions, like hydrogen bonds, π···π, C–H···π, halogen···halogen, aromatic ring···halogen and other non-covalent interactions.2-3 Therefore ligands/systems having more number of such interacting groups -the heterofunctional ligands- are a better bet for forming new architectures. The versatility of heterofunctional ligands to generate special structures, such as nanotubular skeletons, helical motifs and isoreticular three-dimensional structures with tunable large cavities, is commendable but reported infrequently.1,4-12 For that reason, it is a good strategy to explore CPs using hetero functional ligands. The ability of a charged ligand to form tunable H-bonds and modulate its coordination behaviour in presence of different metal ions can provide an effective tool-box to engineer new generations of CPs. It is therefore vital to discern the set of complex electronic information to have structural and temporal control over the assembly formation. The heterofunctional molecule, 2-amino-5-nitrobenzoic acid (L1H) is one such system which got our attention for the following reasons: (i) It has a rigid backbone (aromatic) with given geometry and directionality, which makes it easy to control the desirable topologies. (ii) More than one coordinating sites provided by –NH2, –NO2 and –COO- groups. (iii) Versatile coordination modes of the carboxylate groups in combination with – NO2 groups (iv) sensitivity to acid-base environment of carboxylate and –NH2 groups, which add to structural diversity.9 (v) Possible competition between coordination and H-bonds for –COO- group owing to the presence of –NH2 group ortho to it. (vi) Only four complexes (one with Ag(I) and three with Sn(IV) ions), based on CSD search, are known.13-16

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As all the different coordinating sites,–NH2, –NO2 and –COO- are capable of forming strong H-bonds, the extension of CP due to H-bonding and other intermolecular interactions, is envisaged. Metal nitrobenzoates are well known to coordinate solely through –COO- group, with H-bonding through –NO2 groups or show coordination both through –COO- and –NO2 groups.13-22 Therefore while the formation of CPs owing to diverse coordination modes of –COO- groups, is well expected,23-26 a possible competition between –COO- and –NO2 groups for the metal ions, leaving the other group mainly for H-bonding interactions, cannot be ruled out (Scheme I). It is noteworthy here that, to the best of our knowledge, based upon a CSD search till date no metal nitrobenzoate is known where –NO2 coordinates and –COO-

participates in only H-bonding. Further with –NH2

presenting additional H-bonding site, the outcome of the self-assembled product has to be highly dependent on a fine balance of these non-covalent interactions and their tuning by the metal ion. In continuation of our ongoing efforts27-29 to synthesize crystalline CPs with varied topologies, we report hereby single crystal X-ray structures of six complexes of alkali metal ions. For medium-sized alkali metal ions a role reversal between the coordination and H-bonding nature of –COO- and –NO2 groups, respectively has been observed. Structural diversities observed range from 1D helices and linear threads to 2D brick-wall type or 3D networks. DFT calculations for electron density maps have been performed to supplement and rationalize the crystallographic results.

Experimental Materials and physical measurements All the reagents were commercially available and used as received. The melting points were determined with an electrically heated apparatus. C, H, N elemental analyses were obtained with a CHNS-O analyzer flash-EA-1112 series. The IR spectra of complexes were recorded on Perkin ELMER FTIR spectrometer in the range 4000-400 cm-1. Thermo gravimetric analysis (TGA) data were collected on a NetzschTG-209 instrument. Single crystal structural X-ray diffraction was carried out on a Bruker’s Apex-II CCD diffractometer using Mo Kα (λ = 0.71069 Å) at room temperature.

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General Procedure for the synthesis of complexes (I-V) L1H (1 mmol, 0.182 g) was suspended in a moderate volume of acetonitrilemethanol mixture (10 mL). An aqueous solution of M2CO3 (i.e. Cs2CO3, Na2CO3, K2CO3, Li2CO3) (1 mmol) was added drop wise to this solution and stirred overnight at room temperature. The resulting solution was allowed to slowly evaporate to give orange crystals for complexes (I-III, V), within 1 week (70-78 % yield). M.p.>300 ºC. For complex IV overnight stirred reaction mixture was sealed in a 25 mL Teflon-lined autoclave, which was heated at 120 °C for 72 h. After slow cooling to room temperature for 5 °C/ h, orange colour crystals were obtained.(72 % yield .M.p.>300) Anal. Calcd for (I), C14H11N4O8Cs (%): C, 33.89; H, 2.25; N, 11.29; Found: C, 33.80; H, 2.21; N, 11.27. IR (cm-1) selected bonds: υ = 3407 (s) (O-H), 3292 (m) (NH), 1619 (s) (COO-)asy, 1484 (m) (COO-)sy, 1316 (s) (N-O), 1147 (m) (C-O), 809580 (w) (M-O and M-N). Anal. Calcd for (II), C7H9N2O6Na (%): C, 35.34; H, 3.95; N, 10.63; Found: C, 35.40; H, 3.81; N, 10.49. IR (cm-1) selected bonds: υ = 3389 (b) (O-H), 3281 (m) (N-H), 2912 (w) (Ar-H), 1626 (m) (COO-)asy, 1527 (s) (COO-)sy, 1317 (m) (N-O), 1139 (m) (C-O), 807-508 (w) (M-O). Anal. Calcd for (III), C7H9N2O6K (%): C, 32.84; H, 3.55; N, 10.93; Found: C, 32.70; H, 3.51; N, 10.69. IR (cm-1) selected bonds: υ = 3425 (b) (O-H), 3286 (m) (N-H), 2910 (w) (Ar-H), 1629 (w) (COO-)asy, 1517 (m) (COO-)sy, 1385 (w) (N-O), 1138 (w) (C-O), 805-511 (w) (M-O). Anal. Calcd for (IV), C21H27N6O18K3 (%): C, 32.84; H, 3.55; N, 10.93; Found: C, 32.80; H, 3.51; N, 10.89. IR (cm-1) selected bonds: υ = 3424 (b) (O-H), 3284 (m) (NH), 2911 (w) (Ar-H), 1627 (w) (COO-)asy, 1517 (m) (COO-)sy, 1384 (w) (N-O), 1139 (w) (C-O), 580-525 (w) (M-O). Anal. Calcd for (V), C7H7N2O5Li (%): C, 40.90; H, 3.45; N, 13.63; Found: C, 40.70; H, 3.41; N, 13.79. IR (cm-1) selected bonds: υ = 3478 (b) (O-H), 3311 (s) (N-H), 1609 (w) (COO-)asy, 1534 (m) (COO-)sy, 1442 (w) (N-O), 1136 (m) (C-O), 822507(w) (M-O). Procedure for synthesis of the ionic complex (VI)

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A solution of L1H (1 mmol, 0.182 g)

in aq. ammonia (10 ml) was added to an

aqueous solution (10 ml) of Li2CO3 (1 mmol, 0.074 g) dropwise (pH = 10.38). The resulting solution was allowed to slowly evaporate to give yellowish crystals within 1-2 week (81 % yield). M.p.>300ºC. Anal. Calcd for (VI), C14H24LiN5O13 (%): C, 35.23; H, 5.07; N, 14.67; Found: C, 35.40; H, 4.91; N, 14.79. IR (cm-1) selected bonds: υ = 3482 (s) (O-H), 3311 (sh) (N-H), 2902 (w) (Ar-H), 1608 (sh) (C=C), 1583 (sh) (COO-)asy, 1404 (sh) (COO-)sy, 1539 (m) (N-O)asy, 1292 (m) (N-O)sy, 1143 (w) (C-O), 532 (w) (Li-O). (b = broad, m = medium, s = strong, w = weak).

Theoretical Calculations: The ground-state geometry optimization was carried out applying the density functional theory (DFT) with the Becke three-parameter hybrid exchange functional in concurrence with the Lee-Yang-Parr gradient-corrected correlation function (B3LYP functional) with the 6-311G++(d,p) basis set as implemented in Gaussian 09W. For finding the HOMO-LUMO energy levels, bulk solvent (H2O) effects were approximated by a polarizable continuum model (PCM), using single point energy calculations with B3LYP/6-31++G(d,p). The electrostatic potentials (ESP) mapped on the electronic density surfaces based on the DFT calculations and plotted with the GaussView 5.0 program. Natural Population Analysis (NPA) were calculated using same basis set. AIM calculations: For finding electron density at BCP (Bond Critical Path), Multiwfn program has been applied. The input files (.wfx) were generated by DFT calculations with the same basis set in Gaussian 09W. The contour plots and interacting BCP points were visualized by this software.

X-ray crystallography X-ray data of all these complexes were collected on a Bruker’s Apex-II CCD diffractometer using Mo Kα (λ = 0.71069 Å) at room temperature. The data collected by CCD diffractometer were processed by SAINT correcting for Lorentz and polarization effects.30 An empirical absorption correction was applied using SADABS from Bruker.31 The structures were solved by direct methods, using SIR9231 and refined by full-matrix least squares refinement methods33 based on F2,

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using SHELX-97. All non-hydrogen atoms were refined anisotropically. Phenylene hydrogen atoms were fixed geometrically with their Uiso values 1.2 times of the carbons. Protons of carboxylic acid, water, amino group and ammonium ion were located from the difference Fourier synthesis and were refined isotropically with constraints on their bond distances and with Uiso values 1.2 times that of their carrier oxygen and nitrogen atoms, respectively. All calculations were performed using Wingx package.34 Crystal data and structure refinements for complexes (I-VI) are given in Table 1. Important bond distances (Å) and bond angles (º), and important H-bonding interactions in complexes (I-VI) are given in Table TS1 and TS2, respectively.

Scheme 1. Coordination modes observed for L1, (i) (µ5-κ5, η1:η1:η1:η1:η1) for (I) (ii) (µ2-κ3,η2:η1) for (II)-(IV) (iii) (µ2-κ2, η1:η1) for (V).

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Table 1. Showing structure refinement data of complexes (I-VI) Identification code Empirical formula Formula weight Temperature Wavelength Crystal system Space group Unit cell dimensions

Volume Z Density (calculated) Absorption coefficient F(000) Crystal size Theta range for data collection Index ranges Reflections collected Independent reflections Completeness to theta = 31.65° Absorption correction Max. and min. transmission Refinement method Data / restraints / parameters Goodness-of-fit on F2 Final R indices [I>2sigma(I)] R indices (all data) Largest diff. peak and hole CCDC number

(I) C14H11N4O8Cs 496.18 296(2) K 0.71073 Å Monoclinic C 2/c a = 12.0240(12) Å, α = 90° b = 7.324(8) Å, β = 95.59(6) c = 18.1920(18) Å, γ = 90° 1594.4(3) Å3

(II) C7H9N2O6Na 240.15 296(2) K 0.71073 Å Monoclinic P 21/n a = 6.8127(5) Å, α = 90°. b = 6.9345(7) Å, β = 95.126(4)° c = 20.6971(18)Å, γ = 90° 973.88(15) Å3

(III) C7H9N2O6K 256.26 296(2) K 0.71073 Å Orthorhombic Pnma a = 7.111(4) Å, α = 90° b = 6.888(4) Å, β = 90°. c = 21.267(12) Å, γ = 90°. 1041.7(10) Å3

(IV) C21H27N6O18K3 768.79 296(2) K 0.71073 Å Monoclinic P 2 1/n a = 6.9460(7) Å, α = 90°. b = 21.298(2) Å, β = 91.046(5)° c = 21.227(2) Å, γ = 90°. 3139.7(5) Å3

(V) C7H7N2O5 Li 206.09 296(2) K 0.71073 Å Monoclinic P 21/c a = 4.9113(11) Å, α = 90° b = 28.649(8) Å, β =105.765(14)° c = 6.3322(19) Å, γ = 90° 857.5(4) Å3

(VI) C14H24Li1N5O13 477.32 296(2) K 0.71073 Å Triclinic Pī a = 7.0629(3) Å, α = 67.803(2)° b = 12.1175(5) Å, β = 85.8870(19)° c = 13.2286(6) Å, γ =85.4240(19)° 1043.86(8) Å3

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4

4

4

4

2

2.067 Mg/m3 2.380 mm-1

1.638 Mg/m3 0.179 mm-1

1.634 Mg/m3 0.526 mm-1

1.626 Mg/m3 0.524 mm-1

1.596 Mg/m3 0.135 mm-1

1.519 Mg/m3 0.134 mm-1

968

496

528

1584

424

500

0.12 x 0.09 x 0.07 mm3 2.25 to 30.61°. -16

Role reversal of carboxylate group from coordination to H-bonding

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