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Five new azo-functionalized coordination polymers, namely {[Cd(3,3′-azbpy)(suc)]·(MeOH)}n (1), [Cd(3,3′-azbpy)(msuc)]n (2), {[Cd(3,3′-azbpy)(2,2′-dmglut)(H2O)]·2(H2O)}n (3), {[Cd(3,3′-azbpy)(glut)]·2.5(H2O)}n (4) and {[Co2(3,3′-azbpy)2(tp)(H2O)3]·H2O} (5), have been synthesized from 1,2-di(pyridine-3yl)diazene (3,3′-azbpy) using four different aliphatic and one aromatic dicarboxylic acid salt [succinate (suc2−), methyl succinate (msuc2−), 2,2′-dimethyl glutarate (2,2′-dmglut), glutarate (glut2−) and terephthalate (tp2−)] and two different transition metal salts by the slow diffusion technique at room temperature. The structures of the synthesized compounds 1–5 were characterized by single crystal X-ray diffraction analysis and by elemental analysis, infrared spectroscopy (IR), powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA) and UV–Vis spectroscopy. Compounds 1 and 2 show a honeycomb 3D structure, whereas, compound 3 exhibits a two-dimensional (2D) 2-fold interpenetrating network. Compound 4 shows a wavy 2D sheet structure and compound 5 exhibits a zero dimensional structure which forms a 2D sheet by means of hydrogen bonding, which by further π⋯π interactions forms an overall supramolecular 3D structure. Sorption studies with CO2 and N2 were also done for all the frameworks and a surface characteristic adsorption has been observed.

Highly symmetric enneanuclear copper(II) phosphates [Cu9(Pz)6(μ-OH)3(μ3-OH)(ArOPO3)4(DMF)3] (PzH = pyrazole, Ar = 2,6-(CHPh2)2-4-R-C6H2; R = Me, 2MeAr; Et, 2EtAr; iPr, 2iPrAr; and Ar = 2,6-iPr2C6H3, 2Dip) comprising nine copper(II) centers and pyrazole, hydroxide and DMF as ancillary ligands were synthesized by a reaction involving the arylphosphate monoester, 1, copper(I)chloride, pyrazole, and triethylamine in a 4 : 9 : 6 : 14 ratio. All four complexes were characterized by single crystal structural analysis. The complexes contain two distinct structural motifs within the multinuclear copper scaffold: a hexanuclear unit and a trinuclear unit. In the latter, the three Cu(II) centres are bridged by a μ3-OH. Each pair of Cu(II) centers in the trinuclear unit are bridged by a pyrazole ligand. The hexanuclear unit is made up of three dinuclear Cu(II) motifs where the two Cu(II) centres are bridged by an –OH and a pyrazole ligand. The three dinuclear units are connected to each other by phosphate ligands. The latter also aid the fusion of the trinuclear and the hexanuclear motifs. Magnetic studies reveal a strong antiferromagnetic exchange between the Cu(II) centres of the dinuclear units in the hexanuclear part and a strong spin frustration in the trinuclear part leading to a degenerate ground state.

Anion exchange materials are important for their application in toxic anion control process. Coordination Polymers (CPs) with weakly coordinated anions and lattice anions may be practically useful in anion exchange process. To explore this anion exchange properties by Coordination Polymers (CPs) we have synthesized two water insoluble cationic CPs {[Mn(bix)3(H2O)2].bix.(NO3)2}n (1), {[Cd(bix)2(NO3)2].(H2O)2}n (2) by using N,N-donors linkers bix {bix = 1,4-bis(imidazol-1-ylmethyl)- benzene}. Structure of complex 1 is 1D and contains lattice NO3– anion and the complex 2 is 2D and contains weakly coordinated NO3–anion. Both these complexes along with another previously published structurally similar CP {[Cd(bix)2(NO3)2]}n (3), response in anion exchange studies with foreign anions. All the anion exchange processes have been monitored by FT-IR spectroscopy and PXRD measurements.

Syntheses, structural characterizations, photoluminescence, and adsorption properties of three new azo-functionalized Cd(II)-MOFs, namely, {[Cd(azbpy)(msuc)]·2.5(H2O)}n (2), {[Cd(azbpy)(mglu)]·5(H2O)}n (3), and {[Cd1.5(azbpy)2(glu)]·(NO3)·MeOH}n (4) [where msuc2- = methylsuccinate; mglut2- = methylglutarate; glut2- = glutarate; azbpy = 4,4'-azobispyridine] have been reported. The compounds show different structures only with the variation of aliphatic dicarboxylates. The photoswitching behavior for the above-mentioned newly synthesized Cd(II)-MOFs along with one of our previously reported other azo-functionalized Cd(II)-MOF, namely, {[Cd(azbpy)(suc)]·2(H2O)}n (1), has been studied extensively. At photoilluminated condition, the conductivity values can draw a clear structure-property relationship among the structures of compounds 1-4. Single crystal structural analysis reveals that all the compounds exhibit a three-dimensional (3D) framework connected by azbpy linker and respective aliphatic dicarboxylate through their bis-chelating mono/bis oxo-bridging fashion. Compounds 1-3 exhibit an iso-structural honeycomb like 3D framework showing the same coordination environments, where the metal-carboxylate 2D sheets of compounds 1-3 are pillared by N,N'-donor azbpy linkers. On the other hand, compound 4 exhibits a 2-fold interpenetrated 3D framework with a little difference in its coordination environment and the pillaring of 1D metal-carboxylate ladder by azbpy linkers. All the compounds significantly demonstrate their enhanced sensitivity under light rather than the dark condition. The gas and solvent vapor sorption studies have been performed for the synthesized compounds 2-4. Moreover, compound 2 exhibits an enhanced type IV selective CO2 adsorption isotherm over N2 along with the appearance of gate opening phenomena in that.

Three different N,N′-donor ligands with Zn(NO3)2·6H2O and two different dicarboxylates, flexible succinate (suc) and rigid fumarate (fum) afforded six different metal–organic frameworks (MOFs). Among the N,N′-donor ligands, one bent 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene (3-bpdb) gives two isostructural two-dimensional MOFs, {[Zn(3-bpdb)(suc)]·(H2O)2}n (1) and {[Zn(3-bpdb)(fum)(H2O)2]}n (2). The use of a straight N,N′-donor ligand, i.e., 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene (4-bpdb), results in two three-dimensional (3D) MOFs, {[Zn4(4-bpdb)2(suc)3(OH)2]·5(H2O)}n (3) and {[Zn(4-bpdb)(fum)]·(H2O)2}n (4). Here, 3 is a pillared layer structure, whereas 4 has a 5-fold interpenetrated dimondoid network. For both the bent and straight N,N′-donor ligands an imine alike motif is embedded in the structure. When this motif is replaced by a C–C double bond by using the ligand 1,2-bis(4-pyridyl)ethylene (bpee), it produces two MOFs, {[Zn(bpee)(suc)]2·(H2O)3}n (5) and {[Zn2(bpee)2(fum)2]·(H2O)}n (6), having a...

Assembly of diphenylphosphate (dpp) with Cu(II) salts in combination with the different N-donor linkers, e.g., pentamethyldiethylenetriamine (pmdeta), bis-(3-aminopropyl)amine (bapa) and 4-Picolene (4-pic), yielded three new metal-organic coordination complexes, namely {[Cu(dpp)(pmdeta)] ⋅ClO4.H2O}2 (1), {[{[Cu(dpp)(bapa)H2O] ⋅ClO4} (2) and [Cu(dpp)2(4-pic)2]2 (3) by stirring the constituent reactants at room temperature. Complexes 1–3 were characterized by single crystal X-ray diffraction analysis and were further characterized by elemental analysis, infrared spectroscopy (IR) and powder X-ray diffraction (PXRD) studies. Compound 1 exhibits a dimeric Cu(II) complex which forms a 1D supramolecular chain along the crystallographic c-axis by means of intermolecular π…π interactions. Compounds 2 and 3 form a monomeric and dimeric complex of Cu(II) respectively, which are further extended into a supramolecular 2D structure via C-H.. π interactions for 2 and a 3D structure for 3 with the help of both intermolecular C-H.. π and π…π interactions for 3. In addition, the solid state UV-Vis spectra of compounds 1-3 and free dpp ligand have been investigated at room temperature.

A family of dicyanamide bridged compounds namely {[Co(dca)4(2-abim)2]}n (1), {[Ni(dca)4(2-abim)2]}n (2), {[Cd(dca)4(2-abim)2]}n (3), {[Zn(N(CN)2)2(4-bpdb)]}n (4) and {[Cd(N(CN)2)2(4-bpdb)]}n (5); [where dca = dicyanamide, 2-abim = 2-aminobenzimidazole and 4-bpdb = 1,4-bis-(4-pyridyl)-2,3-diaza-1,3-butadiene] have been synthesized by stirring at room temperature. These compounds have been characterized by single crystal diffraction analysis, infrared spectroscopy (IR) and powder X-ray diffraction (PXRD). Complexes 1–3 are isostructural and exhibit two-dimensional (2D) metal-dca sheet with pendant 2-abim ligand. Compound 4 forms [Zn(N(CN)2)]n chains with a pendent dca and a bridging dca linker, which are further connected by bridging 4-bpdb ligands extending into a 2D layer structure. In case of compound 5 each Cd(II) centers connect with four bridging dca linkers to form [Cd(N(CN)2)]n double chains, which are further connected by bridging 4-bpdb ligands extending into a 2D layer structure. Here [Cd2(N(CN)2)] and 4-bpdb spacer are interpenetrated to each other and resemble polyrotaxane-type structures. Photoluminescent properties of compounds 3–5 were also studied and they exhibit nice ligands based photoluminescence properties at room temperature.

Three new dynamic metal–organic frameworks (MOFs) namely {[Cd2(3,4-pyrdc)2(4,4′-bipy)(H2O)2]·4H2O}n (1), {[Mn2(3,4-pyrdc)2(bpee)(H2O)2]·H2O}n (2), and {[Cu2(3,4- pyrdc)2(bpp)2(H2O)4]·5H2O}n (3), based on 3,4-pyridinedicarboxylate (3,4-pyrdc) and three different N,N′-donor ligands [4,4′-bipyridine (4,4′-bipy), 1,2-bis(4-pyridyl)ethylene (bpee), and 1,3-bis(4-pyridyl)-propane (bpp)] with various divalent transition metal ions have been synthesized and characterized by single-crystal and powder X-ray diffraction and other physicochemical methods. In compounds 1 and 2, the 3,4-pyrdc ligand forms two-dimensional (2D) metal–carboxylate sheets that are connected by N,N′-donor ligands to form three-dimensional (3D) structures with water-filled channels. In compound 3, the 3,4-pyrdc ligand affords one-dimensional metal–carboxylate chains. These chains are connected by the more flexible bpp ligand to form 2D structures, which are extended to a 3D supramolecular architecture by H-bonding. Compounds 1 and 2 show a re...

Five azo-functionalized coordination polymers (CPs), namely, [Zn(azbpy)(NO2-bdc)·H2O]n (1), [Zn(azbpy)(NO2-bdc)]n·3H2O (2), {[Cd(azbpy)(NO2-bdc)·H2O]·2H2O}n (3), {[Mn(azbpy)2(NO2-bdc)]2}n (4), and {[Co(azbpy)(NO2-bdc)(H2O)2][Co(azbpy)0.5(NO2-bdc)(H2O)3]}n (5) have been synthesized using different transition metal salts with 5-nitro-1,3-benzenedicarboxylate (NO2-bdc2–) and 4,4′-azobispyridine (azbpy) ligand using a slow diffusion technique at room temperature. The complexes 1–5 were characterized by single crystal X-ray diffraction analysis, elemental analysis, infrared spectroscopy (IR), powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). In the solid state, compound 1 shows a wavy one-dimensional (1D) ladder; constructed through the N,N′-donor azbpy and NO2-bdc2– ligands with the metal centers, whereas compound 2 exhibits a bilayer two-dimensional (2D) sheet containing a wavy 1D ladder of metal-carboxylate, and compound 3 shows a stairlike wavy 2D sheet. Compound 4 exhibits a novel 2-f...

Two metal–organic frameworks of Cd(II) from 3,4-pyridinedicarboxylate (3,4-pyrdc) and 1,2-bis(4-pyridyl)ethane (bpe) ligands, {[Cd(3,4-pyrdc)(bpe)(CH3OH)]·(H2O)}n (1) and {[Cd(3,4-pyrdc)(bpe)0.5(H2O)]·(H2O)}n (2) have been synthesized by changing the reaction medium. Compound 1 exhibited a 2D structure while compound 2 showed a 3D structure, which have both been revealed by single crystal X-ray studies. Both of the compounds showed interesting solvent mediated reversible structural transformations which have been established by exhaustive X-ray powder diffraction studies, elemental analysis, IR spectroscopy and thermogravimetric analysis. The desolvated form of the 2D framework (1) undergoes an irreversible structural transformation to form the 3D framework (2) upon soaking with water. The 2D to 3D transformation occurs through precise bond rotation and bond breaking which has been established by a GC–MS study. Sorption experiments with different gases and volatiles were performed for both the metal–organic frameworks and clearly indicated the differences in their inherent flexibility and transformability.

Post synthetic modification of coordination polymers have been extensively studied through years, to obtain several marvelous functional materials. Apart from the usual metal or ligand exchange, irreversible structural transformation strategy may also be a useful approach to perform post synthetic modification in coordination polymers for creating functional materials. Considering this approach, three coordination polymer of Zn(II) and Co(II) namely, {[Zn(beb)(dmglut)]}n (1), {Co2(beb)2(hipt)2(H2O)1.5(MeOH)}]n (2) and {[Zn2(beb)2(fum)2]}n (3) (Whereas beb = 1-(2-(1H-benzoimidazol-1-yl)ethyl)-1H-benzoimidazole, dmglut = 3,3′-dimethylglutarate, hipt = 5-hydroxyisophthalate and fum = fumarate) have been synthesized from flexible beb ligand and three different dicarboxylates. Compound 1 and 2 are with a two dimensional structure which are adjoined by weak forces to form a supramolecular three dimensional architecture. Compound 3 has a three dimensional structure with unidirectional channels. Compound 2 and 3 have undergone irreversible structural transformation. These transformations are thoroughly monitored by PXRD analysis, UV–vis spectroscopy, and IR spectroscopy. Solid state emission spectral analyses for two Zn(II) CPs and gas sorption analyses for all the compounds has been also performed.

Three new coordination complexes [Mn(L1)(μ-azide)(azide)]2⋅4H2O (1), [Mn(L1)(fum)]n (2) [L1 = 2methyl-N1,N2-bis(pyridin-2yl)propane-1,2-diamine, fum = Fumaric acid] and [Co(L2)(azide)] (3) [L2 = 6 phenyl-1,3,5-triazine 2,4-diyl amino(pyridine-2yl)methanol] have been synthesized and X-ray crystallographically characterized. Complex 1, a dinuclear Mn(II) complex is formed by bridging azide ligand and other coordination sites are satisfied by tetradentate ligand L1 and terminal azide ligand. The overall structure is an incomplete supramolecular 3D cage structure, formed by intermolecular π … π interaction of pyridyl ligand and hydrogen bonding. Complex 2 comprised of eight coordinated Mn(II) centre where ligand L1 and fumarate is bridged between the metal centers that leads to a one dimensional chain structure which further extended to a 3D structure by π … π and C–H … π interactions. The overall structure is further stabilized by hydrogen bonding with the guest water molecules. Complex 3, a six coordinated mononuclear Co(II) discrete complex is consist of pentadentate ligand L2 and azide act as a terminal ligand. This Mononuclear complex is connected by π … π, C–H … π interactions and hydrogen bonding which ultimately leads to a supramolecular 2D architecture. All the complexes have been further characterized by elemental analysis, infrared spectroscopy (IR) and powder X-ray diffraction (PXRD) studies.

Assembly of 5-nitroisophthalate (nip2−) with first row transition metal salts [Mn(II), Fe(II), Co(II), Zn(II)] in combination with the various neutral auxiliary N,N′-donor linkers, e.g., 2,5-bis-(4-pyridyl)-3,4-diaza-2,4-hexadiene (4-bpdh), 1,3-bis(4-pyridyl)propane (bpp) and 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene (4-bpdb), yielded eight new coordination polymers (CPs), namely {[Mn(4-bpdh)(nip)(H2O)2]·H2O}n (1), {[Fe(4-bpdh)(nip)(H2O)2]·H2O}n (2), {[Co(4-bpdh)(nip)(H2O)2]·H2O}n (3), {[Mn2(bpp)2(nip)2(H2O)2]·H2O}n (4), {[Fe(bpp)(nip)(H2O)]·H2O}n (5), [Zn(bpp)(nip)(H2O)]n (6), {[Fe(4-bpdh)1.5(nip)]·(4-bpdh)0.5}n (7) and {[Fe(4-bpdb)(nip)]·(4-bpdb)0.5(H2O)}n (8) using the slow diffusion technique at room temperature. The complexes 1–8 were characterized by single crystal X-ray diffraction analysis and were further characterized by elemental analysis, infrared spectroscopy (IR) and powder X-ray diffraction (PXRD). Complexes 1–3 are isostructural and exhibit a one-dimensional (1D) metal-carboxylate chain with pendant 4-bpdh ligands, which is further extended into a three-dimensional supramolecular structure by means of H-bonding and π–π interactions. Complexes 4–6 are also isomorphous, but distinctly different from the first three complexes. They exhibit a similar 2-fold interpenetrated three-dimensional (3D) net with 66 dia net topology. Compound 7 displays a two-dimensional (2D) grid-like structure, having 4-bpdh ligands in the crystal void, and this is further extended by means of intermolecular π–π interactions into a 3D supramolecular structure, whereas compound 8 possesses a different 2D grid structure containing free 4-bpdb ligands in the void spaces. The thermal stabilities and UV–Vis spectra of all the complexes and the luminescent properties of complex 6 were also studied.

Single crystal X-ray diffraction of two macrocyclic bischalcones, namely, (2E,25E)-11,17,33,37-tetraoxapentacyclo[36.4.0.05,10.018,23.027,32]dotetraconta-1(42),2,5,7,9,18,20,22,25,27,29,31,38,40-tetradecaene-4,24-dione(1) and (2E,24E)-11,16,32,37-tetraoxapentacyclo[36.4.0.05,10.017,22.026,31]dotetraconta-1(42),2,5,7,9,17,19,21,24,26,28,30,38,40-tetradecaene-4,23-dione(2), each containing a 26-membered ring, has been studied. Compound 1 belongs to the monoclinic system, space group C2/c with a = 34.3615(9) Å, b = 12.7995(3) Å, c = 14.6231(3) Å, β = 96.912(2)°, V = 6,384.6(3) Å3, and Z = 8. Compound 2 is triclinic, space group P-1 with a = 10.066(2) Å, b = 10.670(3) Å, c = 16.590(3) Å, α = 85.95(2), β = 89.244(14), γ = 62.211(13), V = 1572.0(6) Å3, and Z = 2. Intermolecular C–H⋯O hydrogen bonding interactions are present in both compounds.

Seven coordination polymers (CPs) with two types of framework structures, namely, {[M(4-bpdb)(1,3-bdc)]·(4-bpdb)0.5}n [M = Mn (1), Fe (2), and Co (3)], and {[M(4-bpdh)(1,4-bdc)]}n (M = Mn (4), Fe (5), Co (6), and Cd (7)] have been synthesized through the slow diffusion technique using 1,3-bdc and 1,4-bdc ligands with two different azine based N,N′-donor linkers [1,3-bdc = benzene-1,3-dicarboxylate, 1,4-bdc = benzene-1,4-dicarboxylate, 4-bpdb = N,N′-bis-pyridin-4-ylmethylene-hydrazine and 4-bpdh = N,N′-bis-(1-pyridin-4-yl-ethylidene)-hydrazine]. Their structures have been determined by single-crystal X-ray diffraction analysis and further characterized by elemental analysis, IR spectra, and powder X-ray diffraction (PXRD) analysis. Compounds 1–3 are isostructural and feature a two-dimensional (2D) framework structure formed by pillaring the one-dimensional [M(1,3-bdc)]n double chains through 4-bpdb linkers. In all cases of compounds 1–3, free 4-bpdb linkers are present in the lattice and lattice 4-bpdb lig...

Two new isostructural porous coordination polymers of Zn(II) {[Zn2(NH2-bdc)2(4-bpdb)]·(H2O)4}n (1) and {[Zn2(NH2-bdc)2(4-bpdh)]·(H2O)4}n (2) [4-bpdb = 1,4-bis-(4-pyridyl)-2,3-diaza-1,3-butadiene, 4-bpdh = 2,5-bis-(4-pyridyl)-3,4-diaza-2,4-hexadiene and NH2-bdc = 5-amino-1,3-benzenedicarboxylate] have been synthesized using a mixed ligand system by solvent diffusion and structurally characterized through single crystal X-ray diffraction, variable temperature powder X-ray diffraction and thermogravimetric analysis. Both the coordination polymers are constructed using linear Schiff base linkers of similar length having N–N base functionalities but the only difference is the presence of methyl groups in adjacent carbon atoms of the N–N group in the 4-bpdh ligand. Single-crystal structure analysis revealed that both compounds 1 and 2 have two-dimensional (2D) pillared-bilayer framework structures containing 1D channels (8.3 × 3.8 A2 for 1 and 8.0 × 1.6 A2 for 2) filled with lattice water molecules. Channel dimensions in 2 decrease due to the presence of methyl groups. The desolvated frameworks of 1 and 2 are rigid which is evidenced by variable temperature PXRD. Both the compounds show type-I CO2 uptake profiles and the differences in CO2 adsorption uptakes have been corroborated to their void space (27.1% for 1 and 17.1% for 2). Desolvated forms of compound 1 exhibit remarkably high water adsorption capacity even at low vapor pressure whereas desolvated forms of compound 2 show very low water vapor uptake, which could be ascribed to the hydrophobic nature of the pore surface of 2.

Two new Cd(II) coordination polymers, namely [Cd(3-bpdh)2(ClO4)2]n (1) and {[Cd(3-bpdh)(suc)(H2O)]·3(H2O)}n (2), have been synthesized using a substituted bent N,N'-donor ligand 2,5-bis-(3-pyridyl)-3,4-diaza-2,4-hexadiene (3-bpdh) and aliphatic dicarboxylate disodium succinate (suc) with Cd(II) perchlorate salts at room temperature by a slow diffusion technique for the exploration of our previous reported work. Both the structures were determined by single-crystal X-ray diffraction analysis and also by other physicochemical methods. Structure analysis revealed that complex 1 is a 1D chain structure containing coordinated perchlorate with a metal centre, and complex 2 shows a porous 3D framework with encapsulation of lattice water molecules into the void along the crystallographic a-axis. The PXRD study shows the bulk purity of both the complexes and TGA analysis of 2 exhibits that the structure is thermally stable up to 250 °C. Complex 1 shows a nice anion exchange property with replacement of weakly coordinated perchlorate with the inclusion of new anions; and the anion exchanged solids were characterised by FT-IR, PXRD and photoluminescence properties. The desolvated framework of 2 exhibits sorption of CO2 and water vapor and surface adsorption of N2 corroborating with the nature of the pore environment present in 2. The photoluminescence study has been also done for both complexes in the solid state which exhibits ligand based emissions at room temperature.

Figure. In two new complexes of Mn(II) and Zn(II), it has been observed that carboxylate (O)…π interactions played a crucial role in the organization of supramolecular structure and that carboxylate (O)…π interactions also somehow controlled by the C-H…π interactions, which is achieved by proper modulation of the linkers.

Reactions with an aliphatic dicarboxylate (oxalate) as well as an aromatic dicarboxylate (terepthalate) in combination with an N,N′ donor ligand (trans-4,4′-azobispyridine) results two new coordination polymer of divalent manganese, namely {[Mn(azbpy)(H2O)4]·(bdc)·(H2O)2}n, (1) and {[Mn(ox)(H2O)2]·(azbpy)·(H2O)2}n,(2). Both the coordination polymers have one dimensional structure and extended to two-dimension by means of H-bonding. Interestingly, in solid state structure, the hydrogen bonding interaction recognizes the dicarboxylate (bdc) in case of 1 and N donor ligands (azbpy) in 2. The variation in the use of dicarboxylates, creates here a huge variation in the co-ordination modes of the metal ion as well as in the supramolecular structure within the crystal of 1 and 2. The contribution of various types of non-covalent forces are quantitatively explained in the light of Hrishfield surface analysis, which justifies the role of hydrogen bonding in the recognition of the above organic linkers. A DFT calculation of NBO also gives a quantitative understanding of the formation of the solid state structure by H-bonding. A thermogravimetric analysis, solid state fluorescence spectra and EPR spectroscopic study of the complexes have also performed which also nicely corroborated their crystal structures.

Two isostructural coordination polymers based on Co(II) and Ni(II), {[M(azpy)3(p-bdc)2(H2O)4]·(CH3OH)2(H2O)3}n [where M = Co (1) and Ni (2); azpy = N,N′-bis-pyridin-4-ylmethylene-hydrazine and p-bdc = 1,4-benzenedicarboxylate], have been synthesized using mixed ligand systems at room temperature and characterized by single-crystal X-ray diffraction and other physicochemical methods. Structure determination reveals that both the complexes crystallize in the monoclinic space group C2/c and exhibit one-dimensional (1D) ladder like structures constructed by p-bdc and azpy ligands in which Schiff base (azpy) linkers serve as a bridging as well as pendent ligands. These pendent ligands are involved in H-bonding and π–π interactions with lattice water, methanol molecules and bridging azpy ligands, to form the 3D supramolecular structure. Notably, both the frameworks efficiently catalyze the Knoevenagel condensation reactions of a wide range of substituted benzaldehydes with active methylene compounds in heterogeneous medium under environmentally friendly conditions and the products were obtained in excellent yields. These catalysts were also found to exhibit excellent recyclability and re-usability without any significant loss of activity. A variable temperature magnetic study of both compounds was carried out and their magnetic properties justified on the basis of their crystal structure.

Five new mixed ligand coordination polymers, {[Co0.5(H2O)(1,4-bdc)(3-bpdb)Co0.5(H2O)2]·(H2O)3}n (1), [Co(3-bpdh)(1,4-bdc)(H2O)2]n (2), [Zn(3-bpdb)(1,4-bdc)]n (3), {[Zn(3-bpdh)(1,4-bdc)]·(3-bpdh)0.5}n (4) and [Cd(3-bpdb)(1,4-bdc)(H2O)]n (5) [where 3-bpdb = 1,4-bis-(3-pyridyl)-2,3-diaza-1,3-butadiene; 3-bpdh = 2,5-bis-(3-pyridyl)-3,4-diaza-2,4-hexadiene and 1,4-bdc = benzene-1,4-dicarboxylate] were synthesized at room temperature. The structures of 1–5 were determined by single crystal X-ray diffraction analysis and were further characterized by elemental analysis, infrared spectroscopy (IR) and powder X-ray diffraction (PXRD). Compound 1 exhibits a one-dimensional (1D) chain structure with monodentate pendant 1,4-bdc ligands which further extend to a three-dimensional (3D) supramolecular structure by H-bonding and π⋯π interactions. Compound 2 displays a 4-connected two-dimensional (2D) framework with the point symbol {44·62}. Moreover, the 2D structure of 2 is also ultimately packed into 3D supramolecular frameworks through H-bonding and π–π stacking interactions. Compound 3 shows a 5-fold interpenetrated diamondoid net with 66 topology. Compound 4 is a 2D 3-connected net having a point symbol {63} and is extended to a supramolecular 3D structure through C–H⋯π and π⋯π interactions with lattice 3-bpdh ligands. Compound 5 features a 3-fold interpenetrated diamondoid net with 66 topology. The thermal stabilities and luminescent properties of 3–5 were also studied in detail. The complexes exhibit ligands based photoluminescence properties at room temperature.

A solvothermal reaction of cadmium (II) nitrate with succinic acid and isonicotinic acid creates a novel 3D metal-organic framework, [Cd3(isonicotinate)2(suc)2]n(1). Single crystal X-ray structure determination reveals that complex 1 posses two crystallographically independent Cd(II) centres. The succinate anion acts here as a heptadented ligand and binds five Cd(II) centre simultaneously. The heptacoordinated Cd(II) centres are oxo-bridged by succinate moiety and the hexacoordinated metal centres are terminally connected through four different succinate moiety to make the overall 2D sheet arrangement. In unit cell, the ratio of hexadented Cd(II) and heptadented Cd(II) is 1:2. The new compound was also characterized by luminescence spectra and compared with the luminescence spectra of the pure isonicotinic acid.

Ten different metal-organic hybrids of divalent metal ions have been synthesized using the diphenyl phosphate ligand and three different N,N donor spacers. All the complexes have been characterized by single crystal X-ray crystallography and other physico-chemical methods. For six complexes, the diphenyl phosphate (dpp) ligand acts as a bridge between the metal ions, whereas in four complexes dpp acts as a monodentate ligand. All nine complexes (1-9) show two dimensional coordination structures created by the N,N donor spacers, and, the remaining one (10) has a one dimensional ribbon-like structure. Here the aromatic rings present in the compounds viz. phenyl rings of dpp and the pyridyl rings of N,N donor spacers, have a key role to extend the dimensionality in their solid-state structures. In each instance, the aromatic rings of dpp and N,N donor spacers are nicely involved in the supramolecular structure generation by the help of π-π interactions. In all the cases, the role of weak interactions on the crystal packing and their effect in the generation of different supramolecular architectures has been thoroughly investigated. Variable temperature magnetic measurements of three relevant complexes have been carried out. Compounds 1 and 3 clearly indicate the existence of a weak antiferromagnetic interaction between the metal ions through the bridging dpp ligand. In 5, where dpp acts as a monodentate ligand; the metal ion may be considered as an isolated monomer.

Using the same bridging ligand, diphenyl phosphate (dpp), and different co-ligands, 1,10-phenanthroline (phen)/2,2′-bipyridine (bpy), two structurally similar Cu(II) complexes, [Cu(μ-dpp)(phen)(NO3)]2 (1) and [Cu(μ-dpp)(bpy)(NO3)]2 (2), were synthesized. These complexes were characterized by single crystal X-ray diffraction as well as other physico-chemical methods. Both complexes are dinuclear in nature, but complex 1 is extended into a 3D supramolecular architecture by π–π interactions, whereas complex 2 forms a 2D supramolecular layered structure by π–π and C–H…π interactions. We further explored the DNA binding ability of these complexes by an agarose gel electrophoresis study. Although the coordination structures of these two complexes are very similar, complex 1 was found to be more effective at DNA binding. Complex 1 showed a greater cytotoxic effect on the human hepatocellular carcinoma cell line HepG2 compared to complex 2. Moreover, complex 1 induced more S-phase arrest and apoptosis in HepG2 cells than complex 2, as determined by fluorescence activated cell sorters (FACs). Thus our results indicated that changing the co-ligands in copper complexes may rendered an overall change in the supramolecular structure as well as significant variations in the biological activities.

Two new compounds of Mn(II) with the same bridging ligand, trans 4,4′-azobispyridine (azbpy), and different co-ligands, 1,10-phenanthroline (phen) and 2,2′-bipyridine (bpy), have been synthesized and characterized by X-ray crystallography and other physicochemical methods. Although the compounds were prepared under similar reaction conditions, as well as using the same reactant ratios, their compositions and solid state structures are entirely different in the two cases. Compound 1, with [Mn(azbpy)(phen)Cl2]n and [Mn(phen)2Cl2] moieties, constructs a supramolecular 3D self assembly through π–π interactions, whereas in 2 the [Mn(azbpy)(bpy)Cl2]n moiety and the lattice azbpy forms the supramolecular 3D arrangement by both π–π and C–H⋯π interactions. A thermogravimetric study of the complexes and the solid state fluorescence spectra of the ligand and complexes corroborate their structures.

A three-dimensional (3D) robust porous coordination polymer, {[Cu(azpy)(glut)](H2O)2}n (1) (azpy = N,N′-bis-pyridin-4-ylmethylene-hydrazine, glut = glutarate), has been synthesized and structurally characterized. Single crystal X-ray diffraction analysis reveals that each of paddle-wheel Cu2(CO2)4 units is connected with glutarates in the crystallographic bc plane to form a two-dimensional (2D) sheet which is pillared by an azpy linker to afford a 3D porous framework. Controlled heating of the as-synthesized crystal 1 at ∼150 °C under reduced pressure causes a color change of {[Cu(azpy)(glut)]}n (1a) from deep green to light green. The structure determination of the dehydrated compound shows the same framework structure as that of {[Cu(azpy)(glut)](H2O)2}n (1) with the only difference of the nonexistence of lattice water molecules resulting in a large void in the framework. The dehydrated light green crystal 1a regenerates the virgin as-synthesized crystal 1 with the formula of {[Cu(azpy)(glut)](H2O)2}n u...

A three-dimensional (3D) bimetallic (4f−3d) supramolecular framework, {[Nd(pyno)2(H2O)4][Fe(CN)6]·H2O}n (1) (pyno = pyridine-N-oxide), has been synthesized and structurally characterized. Structure...

Two new copper(II) complexes {[Cu(H 2 biim)(H 2 O)(suc)](H 2 O)} n ( 1 ) and {[Cu(H 2 biim) 2 (H 2 O)][Cu(H 2 biim) 2 (glut)](glutH)(NO 3 ) · 2.5H 2 O} n ( 2 ) (H 2 biim, 2,2′-biimidazole; suc, succinate dianion; glut, glutarate dianion) have been synthesized and characterized by single crystal X-ray diffraction study and thermal analysis. Complex 1 comprises of 1D zigzag coordination polymers, elongated along the crystallographic b -axis, connected through H-bonding and face-to-face π–π interactions to form a robust 3D network. Whereas complex 2 is built up of bischelated [Cu(II)(H 2 biim) 2 ] 2+ units, glutarate and nitrate anions and water molecules, held together through an extensive H-bonded system. The resulting 3D supramolecular architecture defines channels which are filled by lattice water molecules and disordered nitrate anions.

Eight new metal-organic hybrid materials of Cu(ll) have been synthesized by using flexible glutarate/adipate as a bridging ligand, 2,2'-bipyridine/1,10-phenanthroline as a chelating ligand, and BF 4 -/Cl0 4 -/Cl- as a counteranion. These materials are characterized by single-crystal X-ray diffraction analyses and variable temperature magnetic measurements. Out of them, complexes 1, 3, 5, and 8 crystallize in the triclinic system with space group P1. Complexes 2, 4, 6, and 7 crystallize in the monoclinic system with space group P2 1 /n (2, 4), F2 1 /c (6), and C2 (7). The structural analysis reveals that bridging glutarate gives rise to dinuclear and tetranuclear species, whereas the adipate dianion leads to octanuclear, one-dimensional and two-dimensional polymeric complexes, although they have been prepared under similar conditions. Supramolecular architectures of higher dimensionality have been achieved through H-bonding and π-π interaction. In all the complexes, the bridging and/or counteranions as well as chelating ligand have a vital role in directing the solid-state structure. A variable temperature (2-300 K) magnetic susceptibility study discloses the antiferromagnetic coupling for all of the complexes.

Three cadmium complexes, [Cd(H2biim)2(SCN)2] (1), [Cd(H2biim)2(SeCN)2] (2) and [Cd(H2biim)2(dca)2] (3) [H2biim = 2,2′-biimidazole; dca = dicyanamide] have been synthesized and characterized by X-ray single crystal structure analysis. In complexes 1 and 2 monomeric units assemble into supramolecular helix whereas in 3 monomeric units assemble into supramolecular 2-D grid with (4,4) net topology. The appearance of helical topology in complexes 1 and 2 is due to the linear nature of SCN−/SeCN− whereas (4,4) net topology in complex 3 is due to the bent nature of dca−. In each case R12(7) hydrogen bonding synthon is attained facilitating the helical and (4,4) net topology.

Six coordination complexes, {[M(H2biim)2(H2O)2]2+X2-}·(nH2O) [(H2biim = biimidazole); {M = Zn (1), Cd (2); X = squarate; n = 2}; {M = Zn (3), Cd (4); X = glutarate; n = 4}; {M = Zn (5), X = succinate; n = 4}; {M = Cd (6), X = succinate; n = 2}], have been synthesized and characterized by X-ray single-crystal structure determination. The crystal packing of all the complexes reveals that cationic [M(H2biim)2(H2O)2]2+ fragments are self-assembled by recognition of enolate/dicarboxylate anions by the uncoordinated N−H motif of H2biim resulting in one-dimensional supramolecular ribbons. The parallel ribbons are stitched across by water-mediated hydrogen bonding and π−π interactions leading to two types of topology: one is a two-dimensional brick wall (1, 2, 6), and the other is a three-dimensional architecture (3−5). In two structures (1, 2) interesting “sandwiched” π−π interactions were observed.

Two new cadmium (II) complexes [Cd(hmt)(dca)2] n (1) and [Cd3(hmt)2(SeCN)6(H2O)2] n (2) (hmt=hexamethylenetetramine, dca=dicyanamide) have been synthesized and characterized by X-ray single-crystal analysis. The complex 1 is a 2D rectangular grid of octahedral cadmium (II) with CdN6 chromophore where cadmium centers are doubly bridged by dicyanamide and hmt along a-axis, which are interlinked by dicyanamide running along c-axis. Whereas, complex 2 is a 1D chain of octahedral cadmium (II) with a three-leg ladder topology running along a-axis. The Cd(II) centers are doubly bridged through SeCN (infinite rail) along a-axis and singly bridged by hmt (two-step rung) along c-axis, having cadmium centers with CdSe2N3O and CdSe2N4 chromophores. The adjacent chains through H-bonding between coordinated water and hmt, and Se $$\cdots$$ Se interaction are extended to 2D supramolecular architecture.

Four cyano bridged Cu(II)–Ni(II) heterometallic complexes of general formula, [{Cu2(L)2Ni(CN)4}(ClO4)2 · xH2O]n (for 1, L = bis(3-aminopropyl) methylamine = medpt and x = 2.5; for 2, L = N-(2-aminoethyl)-1,3-propanediamine = aepn and x = 2; for 3, L = diethylenetriamine = dien and x = 1), [Cu(medien)Ni(CN)4]n (4) (medien = bis(2-aminoethyl)methylamine) have been synthesized and characterized by single-crystal X-ray diffraction analysis and low temperature magnetic study. In complexes 1–3, all the cyanide ligands of tetracyanonickelate(II) take part in bonding, connecting four adjacent copper(II) ions whereas in 4 trans-dicoordinated cyanide of Ni ( CN ) 4 2 - links two Cu(II) ions only. We have already reported, as communication, the structural features of complex 1 and of its dehydrated species 1a. A different chain stereochemistry is detected in the related polymeric frameworks 1–3, mainly dictated by the orientation assumed by the ancillary tridentate L ligand. Thermogravimetric analyses and X-ray powder diffraction of complexes 1–3 reveal that the complexes retain their crystallinity upon removal of lattice water molecules. The magnetic studies of complexes 1–4 were performed in the 2–300 K temperature range. For all the complexes, the χMT values from 300 to 60 K are very close and correspond to isolated Cu(II) ions with different average g values (>2.00). From 60 to 2 K, χMT values decrease indicating weak antiferromagnetic coupling.

The reaction of Cu(ClO4)2 · 6H2O with bis(3-aminopropyl)methylamine and sodium dicyanamide in aqueous medium results in the formation of a dimeric dicyanamide complex of Cu(II), [Cu2(medpt)2(dca)2](ClO4)2. The single crystal X-ray structure reveals that the dinuclear entities are extended to form a supramolecular 1D ladder by H-bonding. Each dinuclear entity is joined to the adjacent unit via the perchlorate anion. Variable temperature magnetic study was performed and the best-fit parameters are J = −1.20 ± 0.02 cm−1, g = 2.08 ± 0.01 with R = 2 × 10−5. These clearly indicate the antiferromagnetic interaction between the Cu(II) center.

A one-pot reaction of CuCl2 · 2H2O and malonic acid leads to a novel three dimensional inorganic–organic hybrid framework, [Na2Cu(mal)2(H2O)2]n, (1) (mal = malonate dianion). Single crystal X-ray structure of 1 reveals that it is a novel heterometallic three dimensional coordination-polymeric network which consists of interlocked anionic Cu–malonate and cationic Na–water–malonate sheets, where malonate dianion functions as an unprecedented heptadentate ligand. Low temperature magnetic study reveals that the compound is weak ferromagnetically coupled and this is supported by magneto-structural correlation. Thermogravimetric analyses are performed and it is observed that complex 1 upon heating finally transforms to CuO, which is evident by X-ray powder diffraction technique. Controlled solid state thermolysis of complex 1 at ∼850 °C for 24 h leads to the formation of CuO nanorods, which is confirmed by scanning electron microscopy and X-ray powder diffraction technique. The nanorods formed here have average diameters of ca. 40–200 nm and lengths up to 13 μm.

Two new polymeric complexes of copper(II), [Cu(L1)(μ-fum)(μ-H2O)]n (1) (fum = fumarate dianion; L1 = N,N′-dimethylethane-1,2-diamine) and [Cu(L2)(μ-tp)]n (2) [tp = terephthalate dianion; L2 = N-(2-aminoethyl)-3-amino-1-propanol], have been synthesized. The molecular structures are determined by X-ray crystallography. Complex 1 is a fumarato-bridged zig-zag 1D chain of CuII−L1, which is extended to a 3D coordination polymer through bridging water molecules. Complex 2 is a chain of CuII in which the terephthalate anions bridge in alternate bis(bidentate) and bis(monodentate) fashions. The coexistence of such types of bridging modes of terephthalate ions in a single molecule is unprecedented. The chelating terephthalate ion is linked to an equatorial and an axial site of consecutive metal ions, while the other terephthalate ion is axially linked to CuII centers. Both the complexes are characterized by variable-temperature susceptibility measurements at room temperature down to 4 K. Fitting of the magnetic data reveals the existence of weak antiferromagnetic interactions through the bridging dicarboxylate pathways. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Three supramolecular networks are synthesized by the combination of Mn(II) and flexible ligands [1,2-bis (4-pyridyl) ethane (bpe); 1,3-bis (4-pyridyl) propane (bpp); 4,4‘-bipyridyl disulfide (bpds)], characterized by single-crystal X-ray analysis. All three complexes have extended solid-state structure formed by π−π interactions, and there is an excellent opportunity to elucidate the difference in the formation of extended networks in these three complexes. Complex 1, which is reported in a paper earlier by our group, is an unprecedented three-dimensional (3D) “honeycomb”-like architecture constructed from a novel sinusoidal one-dimensional (1D) chain [Mn(bpe)(H2O)4]2+ through π−π interactions in which bpe is used as a bidentate bridging ligand. Complex [{Mn(bpp)3Cl2}(H2O)2]n 2 generates a “standing wave”-like architecture by π−π interactions from a neutral zigzag 1D chain of [Mn(bpp)3Cl2]. Complex [{Mn(bpds)2(dca)2(H2O)2}(H2O)4(bpds)]n 3 is a neutral monomer [Mn(bpds)2(dca)2(H2O)2], which is self-assembl...

Four succinato-bridged complexes of copper(II) have been synthesized. Complex 1, [Cu(2)(mu-OH(2))(2)L(bpy)(2)(NO(3))(2)](n) and 2, [Cu(2)(mu-OH(2))(2)L(phen)(2)(NO(3))(2)](n)(bpy = 2,2[prime or minute]-bipyridine; phen = 1,10-phenanthroline and LH(2)= succinic acid) exhibit 1D coordination polymer structures where both the nitrate ions are directly linked to the copper(ii) producing synthons in a 2D sheet. A novel 2D grid-like network, ([Cu(4)L(2)(bpy)(4)(H(2)O)(2)](ClO(4))(4)(H(2)O))n3, is obtained upon changing the nitrate by perchlorate anion in complex 1, where the channels are occupied by the anions. On changing the nitrate by tetrafluoroborate anion in complex 2, a novel octanuclear complex, [Cu(8)L(4)(phen)(12)](BF(4))(8).8H(2)O 4, is isolated. The coligand bpy and phen in these complexes show face-to-face (in 1,2,3,4) or edge-to-face (in 4 )pi-pi interactions forming the multidimensional supramolecular architectures. Interestingly, the appearance of edge-to-face pi-pi interactions in complex facilitates the formation of discrete octanuclear entities. Variable-temperature (300-2 K) magnetic measurements of complexes have been done. Complexes 1 and 2 show very weak antiferromagnetic (OOC-CH(2)-CH(2)-COO) and ferromagnetic coupling (mu-H(2)O). Complex 3 also shows antiferromagnetic (syn-syn mu-OCO), and ferromagnetic coupling (mu-O of the -COO group). Complex 4 with two types (syn-syn and syn-anti) of binding modes of the carboxylate group shows strong antiferromagnetic interaction.

A one pot reaction of MnCl2, acetylene dicarboxylate (C4O42-), and 1,2-bis(4-pyridyl)ethane (bpe) leads to a compound formulated as [{Mn(bpe)(H2O)4}(C4O4)·4.5H2O] and has been shown by single crystal structure analysis to be a three-dimensional network with hexagonal and rhombohedral channels encapsulating C4O42- and water molecules, constructed by the one-dimensional “sinusoidal” [Mn(bpe)(H2O)4]n2+ cationic chains through extensive hydrogen-bonding and π−π interactions.

Three new polymeric squarato-bridged manganese complexes {[Mn(H(2)O)(2)(bpe)(sq)].bpe.H(2)O}(n) (1), [Mn(2)(H(2)O)(4)(phen)(2)(sq)(2)](n) (2) and [Mn(2)(H(2)O)(2)(phen)(4)(sq)].(sq).8(H(2)O) (3) [bpe, 1,2-bis(4-pyridyl)ethane; phen, 1,10-phenanthroline; sq, squarate dianion] have been synthesized and characterized by single crystal X-ray diffraction analysis and variable temperature magnetic studies. Complex 1 is a 2D rectangular grid-like structure, achieved through flexible bpe bridging ligands and squarate dianions. On the other hand the use of chelating phen instead of bpe gives rise to a 1D polymeric chain in complex 2 and to a dinuclear entity in 3. In all the three complexes weak interactions play a vital role in stabilizing the solid-state structure. Variable temperature (2-300 K) magnetic studies indicate weak antiferromagnetic coupling between the metal centres in all the complexes.

Three polymeric Mn(II) complexes, {[Mn(N3)2(bpds)2](bpds)}n (1), {[Mn(N3)2(bpp)3](H2O)}n (2) and [Mn(OCN)2(bpp)2]n (3) [bpds=4,4′-bipyridyl disulfide, bpp=1,3-bis(4-pyridyl)propane] have been synthesized and characterized by single crystal X-ray analysis. Complexes 1 and 2 are 1D coordination polymers, which are extended through weak interactions to 2D sheet in case of 1 and 3D in case of 2. Complex 2 exhibits twofold parallel interpenetrating nets through the formation of H-bonds created by lattice water molecules. The crystal structure of complex 3 shows twofold parallel interpenetrating layers based on a 4,4 topology. The variable temperature magnetic study exhibits weak antiferromagnetic interactions between the metal centers in all the complexes.

Two new dicyanamido-bridged polymeric complexes of manganese(II), [Mn(dca)2(pic)2]n 1 and [Mn(dca)2(biim)]n 2 (dca = dicyanamide, pic = 4-picoline, biim = 2,2‘-biimidazole), have been synthesized a...

Two new polymeric azido-bridged manganese complexes of formulas [Mn(N3)2 (bpee)]n (1) and {[Mn(N3)(dpyo)Cl(H2O)2](H2O)}n (2) [bpee, trans-1,2-bis(4-pyridyl)ethylene; dpyo, 4,4'-dipyridyl N,N'-dioxide] have been synthesized and characterized by single-crystal X-ray diffraction analysis and low-temperature magnetic study. Both the complexes 1 and 2 crystallize in the triclinic system, space group P1, with a = 8.877(3) A, b = 11.036(3) A, c = 11.584(4) A, alpha = 72.62(2) degrees, beta = 71.06(2) degrees, gamma = 87.98(3) degrees, and Z = 1 and a = 7.060(3) A, b = 10.345(3) A, c = 11.697(4) A, alpha = 106.86(2) degrees, beta = 113.33(2) degrees, gamma = 96.39(3) degrees, and Z = 2, respectively. Complex 1 exhibits a 2D structure of [-Mn(N3)2-]n chains, connected by bpee ligands, whose pyridine rings undergo pi-pi and C-H...pi interactions. This facilitates the rare arrangement of doubly bridged azide ligands with one end-on and two end-to-end (EO-EE-EE) sequence. Complex 2 is a neutral 1D polymer built up by [Mn(N3)(dpyo)Cl(H2O)2] units and lattice water molecules. The metals are connected by single EE azide ligands, which are arranged in a cis position to the Mn(II) center. The 1D zipped chains are linked by H-bonds involving lattice water molecules and show pi-pi stacking of dpyo pyridine rings to form a supramolecular 2D layered structure. The magnetic studies were performed in 2-300 K temperature range, and the data were fitted by considering an alternating chain of exchange interactions with S = 5/2 (considered as classical spin) with the spin Hamiltonians H = -Ji sigma(S(3i)S(3i+1) + S(3i+1)S(3i+2)) - J2 sigmaS(3i-1)S(3i) and H = -Ji sigmaS(2i)S(2i+1) - J2 sigmaS(2i+1)S(2i+2) for complexes 1 and 2, respectively. Complex 2 exhibits small antiferromagnetic coupling between the metal centers, whereas 1 exhibits a new case of topological ferromagnetism, which is very unusual.

Three polymeric cobalt(II) complexes of formulae [Co(pyo)2(dca)2]n (1), [Co3(ac)4(bpe)3 (dca)2]n (2) and [{Co(male)(H2O)2(H2O)]n (3) [pyo, pyridine-N-oxide; dca, dicyanamide; ac, acetate; bpe, 1,2-bis-(4-pyridyl)ethane and male, maleate] have been synthesized and characterized structurally as well as magnetically. The structure determination of complex 1 shows that each octahedral Co(II) in the 1D coordination chain is attached with four μ-1,5-dicyanamide and two pendant pyridine-N-oxide ligands, which form mutual relationships with other 1D chains through non-covalent π-π interactions, giving rise to a 2D infinite sheet-like structure. The molecular structure reveals that complex 2 adopts an infinite three-leg ladder-like structure in which three parallel 1D Co(bpe) chains are connected by syn-syn and oxo bridging acetate ligands. The dicyanamide ligands are pendant to the terminal Co(II) centers. Complex 3 is an infinite 3D network in which carboxylate groups of the maleate ligand are linked to Co(II) centers in syn-anti fashion. The structure of complex 3 has already been reported. The variable temperature (300–2 K) magnetic measurements have been performed for all three complexes. In the case of 2, the full structure can be rationalized as quasi-isolated trimers; the exchange Hamiltonian that describes magnetic interactions between the effective S′ = 1/2 spins, at low temperature is . Fixing g⊥ = 6.01 and g∣∣ = 2.25, according to the EPR measurements at 4 K, 2J = −3.3 cm−1 is the best-fit parameter. For 1 and 3, complete fits are not possible for calculating the corresponding J parameters for the one- and three-dimensional structures, respectively. Only an approximate J value has been calculated for 1.

Two new polynuclear complexes of Cu(II), [(μ-1,1,3-N3)2{Cu2(me2tn)2(N3)2}]n (1) (me2tn=2,2-dimethylpropane-1,3-diamine) and [Cu2(μ-C2O4)(μ-N3)(ipr2en)2]n(ClO4)n (2) (ipr2en=N,N′-di-isopropylethane-1,2-diamine) have been synthesized and structurally characterized by X-ray crystallography. The crystal structure of 1 displays a 2D network in which distorted octahedral copper(II) centers, chelated by a me2tn ligand and bound to a terminal azide, are connected through μ-1,1,3 bridging azide anions. The structure of 2 shows 1D chains comprising alternating [(ipr2en)Cu-Ox-Cu(ipr2en)] units and end-to-end azide ligand. The chains on mutual H-bonding interaction through ClO4 −, give rise to a 2D supramolecular architecture. The magnetic data of complexes were recorded in the temperature range, 300–2 K. In case of complex 1, the magnetic data are consistent with a ferromagnetic interaction through the end-on azide bridge (JFM=10 cm−1) and a weak antiferromagnetic interaction (zj=−0.8 cm−1) between the ferromagnetically coupled dimers and an average g-value of 2.05. The susceptibility data of 2 were fitted using an alternating AF–AF chain spin 1/2 law which leads to the following parameters Joxalate=−180 cm−1, Jazide=−43 cm−1 and g=2.25 cm−1.

Dicarboxylate supported metal organic hybrids of Co(II), Zn(II) and Cd(II) have been synthesized using two different pyridyl based N,N′ linkers having Schiff base functionalized site. The use of flexible dicarboxylate glutarate in designing such frameworks has created a marked diversity in topology. The different N,N′ donor linkers also played an active part in the channel modification in the synthesized MOFs. The structural and topological diversity has been analyzed from the single crystal X-ray structure. Five compounds, {[Co(azpy)(glut)]·(CH3OH)}n (1), {[Co(meazpy)(glut)(H2O)2]·(H2O)3}n (2), {[Zn(azpy)0.5(glut)(H2O)]·(azpy)0.5}n (3), {[Zn(meazpy)0.5(glut)(H2O)]·(H2O)2}n (4) and {[Cd(azpy)(glut)]·(CH3OH)}n (5), show porous structures with solvent accessible voids. The nature of the pores as well as the existence of lattice solvent molecules in 1 and 2 are different due to the use of a different pillar ligand in their fabrication. In case of 3 and 4 there are some nice effects of non-covalent interaction in the construction of their solid state structure, which has also originated by the change of pillar N,N′ donor linkers. Complex 5 is topologically as well as structurally similar to 1 forming a 2D-grid like structure. In {[Cd2(meazpy)2(glut)(NO3)]2}n (6) there is a formation of 2D sheets with the coordinated counter anion. Interestingly, here the sheets are disposed in a perpendicular fashion to each other and do not contain any solvent accessible void. Upon removal of the solvent molecules, the frameworks 1–5 show moderate CO2 and H2 uptake at 273 K and 77 K, respectively. The desolvated frameworks show different quantities of CO2 and H2 uptake which has been corroborated to their structures.

Three new metal–organic hybrids have been synthesized in a reaction of Cd(II) with 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene (3-bpdb) and disodium succinate (Na2suc). All three compounds, i.e., {[Cd(3-bpdb)(Cl)]·ClO4}n (1), {[Cd(3-bpdb)3(H2O)2]·(3-bpdb)(ClO4)2}n (2) and {[Cd(3-bpdb)(suc)(H2O)2]·(H2O)2}n (3) are characterized by single-crystal X-ray diffraction and other physicochemical methods. Structure determination reveals that 1 shows an α-polonium type 3D coordination network created by an exactly perpendicular Cl–Cd–Cl linkage. The framework of 1 contains 1D channels, which are filled with ClO4−. Compound 2 shows a 1D coordination structure with two bridging and two pendent 3-bpdb ligands. These pendent ligands are involved in H-bonding, π–π and C–H⋯π interactions with its coordinated water molecules and lattice 3-bpdb ligands, to form the 3D supramolecular structure. Compound 3 is a 2D 4-connected net with succinate and the 3-bpdb ligand and extended to 3D supramolecular architecture by H-bonding and π–π interactions. During the syntheses, an in situ chemical transformation of perchlorate to chloride has occurred along with the oxidation of imine to amide and the chlorides so produced are found integrated in compound 1, which facilitates the oxidation of imine in a very unprecedented way.

A 2-D croconato bridged complex of Cu(II), [{Cu(C5O5)(bpee)}·0.5H2O]n (1) [bpee, trans-1,2-bis(4-pyridyl)ethylene] has been synthesized by in situ hydrothermal reaction and characterized by X-ray diffraction analysis, variable temperature magnetic susceptibility measurement and EPR study. The structure determination reveals that the adjacent 2-D sheets are extended to 3-D supramolecular architecture through π–π and trifurcated C–H⋯O interactions, which inhibit the oxygen atom of croconate from forming the usual bridging mode.

A novel 2D rectangular grid coordination polymer with a mixed valence localized copper(I/II), [Cu2ICuII(pyz)2(C5O5)2 (H2O)2]n (pyz, pyrazine; C5O52−, croconate dianion) has been hydrothermally synthesized viain situ redox reaction of Cu(II), and characterized by X-ray diffraction analysis, magnetic and EPR study. The structure extends to a 3D supramolecular network through H-bonding.