Search

Condensation of N,N-dimethyl-1,3-diaminpropane with salicylaldehyde, 3-methoxysalicylaldehyde and 3-ethoxysalicylaldehyde produces three Schiff bases, HL1 [2-(3-(dimethylamino)propylimino)methyl)methoxyphenol], HL2 [2-(3-(dimethylamino)propylimino)methyl)-6-methoxyphenol], and HL3 [2-(3-(dimethylamino)propylimino)methyl)-6-ethoxyphenol ] , respectively. Addition of cadmium(II) chloride to the methanol solution of the tridentate Schiff base, HL1, produces phenoxo-bridged dinuclear cadmium(II) complex, [Cd2(L1)2(Cl)2] (1). Similarly, addition of cadmium(II) nitrate to the methanol solution of the tetradentate Schiff base, HL3, produces phenoxo-bridged dinuclear cadmium(II) complex, [Cd2(L3)2(NO3)2] (3). On the other hand, [Cd(L2)2Cd(NCO)2] (2), is produced by the addition of cadmium(II) perchlorate into the methanol solution of tetradentate Schiff base, HL2 followed by the addition of sodium cyanate. Structures of the complexes have been confirmed by single crystal X-ray diffraction studies. All complexes are dinuclear with Cd2O2 cores. Complex 1 contains square pyramidal cadmium(II) centres, whereas complexes 2 and 3 contain octahedral cadmium(II) centres. All three complexes show fluorescence.

Two copper(II) complexes, [Cu2L2(μ1,1-N3)2]·2CH2Cl2 (1) and [CuL(μ1,5-dca)]n (dca = dicyanamide) (2) have been synthesized using a tridentate Schiff base ligand, 1-[(3-methylamino-propylimino)-methyl]-naphthalen-2-ol (HL) and azide or dicyanamide as co-ligand. Both complexes are characterized by elemental analysis, IR and UV–Vis spectroscopy and single crystal X-ray diffraction studies. The coordination geometry around the copper center in complex 1 is as an elongated (4 + 1) square pyramid and that in complex 2 is square planar with the tridentate Schiff base ligand in the basal plane. Complex 1 is a centrosymmetric dimer in which metal centers are connected by the double μ-1,1-azido bridges. On the other hand, complex 2 is a 1D zigzag chain in which metal centers are connected by μ1,5-N(CN)2 ligands. The catecholase like activity for both complexes have been studied by using 3,5-di-tert-butylcatechol (3,5-DTBC) as the substrate. Complex 1 shows higher activity (kcat = 40.8 h−1) than that of complex 2 (27.6 h−1) towards such oxidation reaction.

A copper(II) complex, [Cu2(L)2(N3)2] [where HL = 2-((3-(methylamino)propylimino)methyl)-6-methoxyphenol] has been synthesized and characterized by elemental analysis, IR, UV–vis and fluorescence spectroscopy, and single-crystal X-ray diffraction studies. The complex crystallizes in the trigonal space group R. The deprotonated tridentate Schiff base occupies three coordination sites of copper(II). The fourth coordination site is occupied by an azide. A symmetry-related azide from a different molecule coordinates with the fifth site of copper(II), thereby forming a double end-on azide-bridged centrosymmetric dimer. Variable temperature solid–state magnetic studies between 2 and 300 K were carried out and the data indicate predominant antiferromagnetic exchange interactions with 2J = –0.45 cm−1. The magnetic field-dependent magnetization study (M − H) reveals existence of antiferromagnetic ordering at a lower temperature (2 K) with a very small coercive field (~20 Oe) suggesting soft magnet behavior of the c...

The 1:1 condensation of N,N-dimethyl-1,3-diaminoethane with 5-bromosalicylaldehyde, 3-methoxysalicylaldehyde and 3-ethoxysalicyalaldede produces three Schiff bases, HL1 [2-(-(3-(dimethylamino)propylimino)methyl)-4-bromophenol], HL2 [2-(-(3-(dimethylamino)propylimino)methyl)-6-methoxyphenol] and HL3 [2-(-(3-(dimethylamino)propylimino)methyl)-6-ethoxyphenol], respectively. Addition of zinc(II) perchlorate to the methanol solution of HL1 produces a phenoxo bridged dinuclear zinc(II) complex, [Zn2(HL1)4](ClO4)4 (1), where the potential tridentate N2O donor Schiff base, HL1, is trapped in its zwitterionic form and behaves like a bi-dentate ligand. On the other hand, phenoxo bridged dinuclear complexes, [(HL2)Zn2(L2)(dca)2]ClO4 (2) and [(HL3)Zn2(L3)(NCS)2]ClO4·CH3OH (3) are produced by the addition of zinc(II) perchlotate into the methanol solutions of the potential tetradentate Schiff bases, HL2 and HL3, respectively, followed by the addition of sodium dicyanamide or sodium thiocyanate. In both complexes, Schiff bases are trapped in their deprotonated anionic forms and non-deprotonated zwitterionic forms as well. The deprotonated ligands are coordinated in their usual chelating tetradentate manners whereas zwitterionic forms of the non-deprotonated ligands are coordinated to zinc(II) only through the imine nitrogen and phenoxo oxygen, i.e., they behave as bi-dentate ligands. The structures of the complexes have been confirmed by single crystal X-ray diffraction studies. All three complexes are dinuclear and contain Zn2O2 cores. All three complexes show fluorescence.

Three new cadmium(II) complexes, [Cd(dede)(μ-1,3-N 3 )(μ-1,1-N 3 )] n ( 1 ), [{Cd 3 (L 1 ) 2 (μ-1,1-N 3 ) 4 (CH 3 OH) 2 }·2CH 3 OH·2H 2 O] n ( 2 ) and [(CdL 2 ) 3 (μ-1,1,1-OH)][(CdL 2 ) 3 (μ-1,1,1-N 3 )](ClO 4 ) 4 ·H 2 O ( 3 ) {dede = N,N-diethyl-1,2-diaminoethane, HL 1 = 2-(2-((diethylamino)ethylimino)methyl)phenol and HL 2 = 2-(2-((diethylamino)ethylimino)methyl)-6-methoxyphenol, have been prepared and characterized by elemental and spectral analysis. Structures of complexes have been confirmed by single crystal X-ray diffraction studies. Complex 1 contains alternating double μ-1,1- and μ-1,3-azide bridges and creates two-dimensional sheet with 6 3 -hcb topology. Complex 2 consists of μ-1,1-azide bridged chain and forms three-dimensional architecture via hydrogen bonding interactions. Complex 3 has a partial cubane [Cd 3 O 4 ] core consisting of trinuclear cadmium(II) moieties. The variation in the denticity of ligands causes changes in molecular and crystalline architectures of the complexes. All the three complexes show fluorescence.

Two mononuclear cobalt(III) Schiff base complexes with azide [Co(L)(N3)(L0 )] (1) and [Co(L)(N3)(L00)] (2) {where HL ¼ 1-((2-(diethylamino)ethylimino)methyl)naphthalene-2-ol, HL0 ¼ 2-hydroxy-1-naphthaldehyde and HL00 ¼ acetylacetone} have been synthesized and characterized by elemental analysis, IR and UV-Vis spectroscopy and single crystal X-ray diffraction studies. Both complexes show mononuclear structures with azide as terminal coligand. Structural features have been examined in detail that reveal the formation of interesting supramolecular networks generated through non-covalent forces including hydrogen bonding, C–H/H–C and C–H/p interactions. These interactions have been studied energetically by means of theoretical DFT calculations. We have also analyzed the unexpected O/O interactions observed in one complex between the oxygen atoms of the coordinated aldehyde groups using several computational tools, including Bader's “atoms-in-molecules” (AIM) and natural bond orbital (NBO) analyses. peerReviewed

Two enantiomorphic (P and M) helical coordination polymers of [Cu(μ1,3-N3)(L)]n {HL = 2-(dimethylamino)ethyliminomethylnaphthalen-2-ol} have been synthesized by the self-assembly of the achiral precursors via spontaneous resolution. The structures have been confirmed by single crystal X-ray crystallography. Solid-state circular dichroism spectra have confirmed the chirality of both P and M helical chains.

Three copper(II) complexes, [Cu(L1)(H2O)(OClO3)]n (1), [Cu(L1)(N3)] (2) and [Cu(L2)(Cl)(H2O)] (3) [HL1 = 4-chloro-2-((quinolin-8-ylimino)methyl)phenol and HL2 = 2-ethoxy-6-((quinolin-8-ylimino)methyl)phenol], have been synthesized and characterized by elemental analyses, IR and UV–Vis spectroscopy and single-crystal X-ray diffraction studies. The theoretical study, carried out using density functional theory (DFT) calculations, is devoted to the analysis of the interesting supramolecular assemblies in the solid state of the structures, paying especial attention to lp –π and π–π interactions involving the quinolin-8-ylimino moiety.

Three copper(II) complexes, [Cu2(L)2(μ1,1-N3)2] (1), [Cu2(L)2(μ1,1-NCO)2] (2) and [Cu(L)(μ1,5-dca)]n (3), where HL is a tridentate mono-condensed Schiff base, 1-(2-aminoethyliminomethyl)naphthalen-2-ol, and dca is dicyanamide, have been prepared and characterized by elemental analysis, IR, UV–Vis and fluorescence spectroscopy and single crystal X-ray diffraction studies. The Schiff base ligand was prepared by a counter anion mediated copper(II) templated synthesis. The azide ligand in complex 1 and the cyanate ligand in complex 2 show μ-1,1 bridging modes, whereas the dca ligand shows the μ-1,5 bridging mode in complex 3. Three equatorial positions of copper(II) are occupied by the tridentate Schiff bases in all three complexes. The fourth equatorial sites are occupied by nitrogen atoms of azide in 1, cyanate in 2 and dca in 3. Another nitrogen atom from a symmetry related pseudohalide coordinates in the axial position of copper(II) to complete its square pyramidal geometry in each of the complexes. Significant supramolecular interactions are observed in all the complexes. Variable temperature magnetic measurements indicate antiferromagnetic interactions between the copper(II) centers in all three complexes.

Two new bis(μ-tetrazolato-NN′) bridged dinuclear nickel(II) Schiff base complexes [Ni2L12(PTZ)2]·2(CH3)2SO·2.69H2O (1) and 2[Ni2L22(PTZ)2]·3H2O (2) (HL1 and HL2 are Schiff bases, HL1 = 2-((2-(dimethylamino)ethylimino)methyl)phenol, HL2 = 2-((2-(methylamino)ethylimino)methyl)-6-methoxyphenol and HPTZ is 5-pyrazinyltetrazole) have been synthesized via [3+2] cyclo-addition of 2-cyanopyrazine and sodium azide in presence of nickel(II) acetate tetrahydrate and the respective Schiff bases. The structures of the complexes are confirmed by single crystal X-ray diffraction analysis. Both complexes show fluorescence. The change in the denticity of the Schiff base blocking ligand is shown to have no effect in controlling the molecular structures of the complexes. The supramolecular self assemblies are also explored.

A homochiral helical coordination polymer of copper(II) has been synthesized using achiral precursors via spontaneous symmetry breaking and has been confirmed by single crystal X-ray diffraction and solid-state CD spectroscopy. The variable temperature magnetic measurements indicate the presence of weak ferromagnetic exchange interactions mediated by end-to-end cyanate bridges (J = +0.12 cm(-1)).

Three new heteronuclear nickel(ii)/cadmium(ii) complexes, [(SCN)(Cl)Cd(L)Ni(DMF)2] (1), [(SCN)(CH3CO2)Cd(L)Ni(CH3OH)2] (2) and [(SCN)(Cl)Cd(L)Ni(NH2CH2CH2CH2NH2)]n (3) {where H2L = N,N'-bis(3-ethoxy-salicylidene)propane-1,3-diamine is a N2O4 compartmental Schiff base}, have been synthesized and characterized. The structures of the complexes have been confirmed by single crystal X-ray diffraction studies. In each complex, nickel(ii) is placed in the inner N2O2 environment and cadmium(ii) is placed in the outer O4 compartment of the compartmental Schiff base. Furthermore, the importance of unconventional C-Hπ (chelate) interactions in the solid state of both complexes and C-Hπ (thiocyanate) interaction in complex 2 has been described by means of DFT and MEP calculations and characterized using NCI plots. All complexes show photoluminescence at room temperature upon irradiation by ultraviolet light. The lifetimes of excited states are in the range of 2-6 ns.

A dinuclear copper(II) complex, [(CH3CN)Cu(L)2Cu](ClO4)2, has been synthesized by reacting an oxime-based tridentate Schiff base ligand, 3-[2-(dimethylamino)-ethylimino] butan-2-one oxime (HL), with copper(II) perchlorate hexahydrate. The complex has been characterized by elemental and spectral analyses. Structure of the complex has been confirmed by single crystal X-ray diffraction technique. The complex may be used as moderate catalyst for the oxidation of o-aminophenol to 2-aminophenoxazine-3-one.

Correction for ‘Diminishing accessibility of electrophilic nickel(ii) centres due to incorporation of a methylene spacer in the pendant side arm of a series of heterotrinuclear nickel(ii)/sodium complexes: a DFT study using a homodesmotic equation’ by Prasanta Kumar Bhaumik et al., CrystEngComm, 2020, 22, 2970–2977, DOI: 10.1039/D0CE00251H.

This paper describes the one-pot synthesis of two CuBr based coordination polymers, {[Cu(μ2-L1)Br]·1.87H2O}n (1) and {[Cu(μ2-L2)Br]·C4H10O}n (2), where L1 = 2,3-dihydro-5,6-bis(4-methoxyphenyl)pyrazine and L2= 5,6-diphenyl-2,3-dihydropyrazine, upon reduction of copper(II) at ambient conditions. The structures have been confirmed by single crystal X-ray diffraction analysis. Both complexes are found to be highly inert toward oxidation. Finally, a density functional theory (DFT) study of the energetic features of several noncovalent interactions observed in the solid state has been analyzed and characterized using Bader’s theory of “atoms in molecules” and the cuprophilic interactions in complex 2 using natural bond orbital methodology.

Three copper(I) complexes [Cu(µ2-L1)I]n (1), [CuL1(µ-1,1,3-SeCN)]n (2) and [Cu2(µ2-I)2(L2)2] (3), where L1 = 5,6-diphenyl-2,3-dihydropyrazine and L2 = 2,3-dihydro-5,6-bis(4-methoxyphenyl)pyrazine, have been synthesized via in situ reduction of copper(II) precursors under ambient conditions and they have been characterized by elemental analysis, IR and UV–Vis spectroscopy and single-crystal X-ray diffraction studies. The copper(I) centres have trigonal planar geometries in complexes 1 and 3, whereas it is tetrahedral in complex 2. Complex 1 has a 1-D chain structure, complex 2 features a ladder-like polymeric coordination network with Cu2Se2 core, complex 3 features a double iodide bridge dimer. Complex 1 crystallizes in monoclinic space group P21/c whereas complexes 2 and 3 crystallize in triclinic space group P1−1. Complexes 1 and 2 show significant C-H···π interactions, but complex 3 has no such C–H⋯π interactions.

Addition of an aqueous methanol solution of nickel(II) acetate tetrahydrate into a methanol solution of the tridentate Schiff base, 3-(methylamino)propyliminomethylphenol (HL), resulted in the solid-state isolation of an octahedral nickel(II) complex [Ni(L)2]·3H2O, where lattice water molecules formed hydrogen-bonded water tetramers, which were connected among themselves to form a T4(1) tape. The tape, stabilized by hydrogen bonding interactions with the nickel(II) complex, was characterized by X-ray diffraction studies, FTIR, and thermo-gravimetric (TG) analyses. When thermally decomposed, the water loss was irreversible.

Five cadmium(II) complexes, [Cd(PZTZ)2(OH2)2] (1), [Cd2(L1)2(Cl)2]·0.11CH3OH (2), [Cd(PRTZ)(L1)(OH2)] (3), [Cd(PRTZ)(L2)(OH2)] (4) and [Cd(PZTZ)(L2)(OH2)]·0.25H2O (5) {HL1 = 2-(3-(methylamino)propylimino)methyl)phenol; HL2 = 2-(3-(dimethylamino)propylimino)methyl)phenol; HPZTZ = 2-pyrazinyltetrazole and HPRTZ = 2-pyridyltetrazole} have been synthesized and characterized. Single crystal X-ray diffraction studies have confirmed the structures of the complexes. Complex 2 crystallizes in triclinic space group P 1 ¯ , and all others crystallize in monoclinic space group P21/c. Complex 1 consists of a discrete centrosymmetric mononuclear unit, in which cadmium(II) is octahedrally coordinated by two pyrazene and two tetrazolate nitrogen atoms of two PZTZ− moieties and two oxygen atoms of two water molecules. The asymmetric unit of complex 2 contains a double phenoxo bridged dinuclear cadmium(II) species and 0.11 fraction of a methanol molecule. In the dinuclear unit, each cadmium(II) is penta-coordinated. In each of the complexes 3, 4 and 5, cadmium(II) is coordinated meridionally by a depronated terdentate Schiff base {(L1)− for 3 and (L2)− for 4 and 5} and two nitrogen atoms of the (PRTZ)− in 3 and 4 and two nitrogen atoms of the (PZTZ)− in 5. Water molecules coordinate in the sixth coordination sites of cadmium(II) in the complexes to complete their distorted octahedral geometries. All the complexes show photoluminescence in DMSO solution at room temperature upon the irradiation of ultraviolet light. The life times of the excited states are in the range of 8.32–12.22 ns. Weak interactions like C–H⋯π/O–H⋯π/π⋯π with multiple hydrogen bonds promote the formation of supramolecular architectures in these complexes.

A 2-D coordination polymer, [Cu(1,2-en)2(μ3-I)2Cu2(μ2-I)2]n (1), was formed at room temperature by in situ insertion of [Cu(1,2-en)2]2+ guests into 1-D chains of a [Cu2I4]2− host [1,2-en = 1,2-diaminoethane]. The structure of the complex was confirmed by single-crystal X-ray diffraction study. The shortest copper(I)–copper(I) distance within the complex is 2.89 A.

Two new copper(II) complexes, [Cu(L)(OCN)] ( 1 ) and [CuL(dca)] n ( 2) , where HL = 2-(-(2-(diethylamino)ethylimino)methyl)naphthalen-1-ol, dca = N(CN) 2 − , have been synthesized and characterized by elemental analysis, IR, UV–VIS spectroscopy and single crystal X-ray diffraction studies. Complex 1 has square planar and complex 2 square pyramidal geometries in solid state around metal centre. Interactions of the complexes with calf thymus DNA (CT DNA) were studied by UV–VIS spectroscopy. Binding constant and site size of interaction were determined. Binding site size and intrinsic binding constant K revealed complex 1 interacted with calf thymus DNA better than complex 2.

Two nickel(II) complexes, [Ni(L)(2)] (1) and [Ni-2(mu(1,1)-N-3)(2)(L)(2)(DMSO)(2)] (2) [where HL = 3-(methyl-amino)propyliminomethyl-4-bromophenol, a tridentate Schiff base], have been synthesized and characterized by elemental analysis, IR, UV-Vis and fluorescence spectroscopy and single-crystal X-ray diffraction studies. The deprotonated tridentate Schiff base occupies three coordination sites of nickel(II) in each of the complexes. In the absence of any secondary coordinating anions, the octahedral geometry of nickel(II) in complex 1 is completed by the coordination of a second molecule of the tridentate Schiff base. On the other hand, in complex 2, the fourth coordination site of nickel(II) is occupied by an azide. A symmetry related azide from a different molecule coordinates the fifth site of nickel(II), thereby forming a double end-on azide bridged centrosymmertric dimer. An oxygen from a DMSO molecule occupies the sixth coordination site of nickel(II) to complete its octahedral geometry. There are hydrogen bonding and C-H center dot center dot center dot pi interactions within the dinuclear moiety of complex 2. A one-dimensional chain along the a axis is produced in complex 1 via a Br center dot center dot center dot Br interaction. (C) 2014 Elsevier Ltd. All rights reserved. (Less)

Four new mono-nuclear square planar nickel(II) complexes [Ni(L)(N3)] (1), [Ni(L)(NCO)] (2), [Ni(L)(NCS)] (3) and [Ni(L)(NCSe)] (4), where HL = 2-(1-(2-(diethylamino)ethylimino)ethyl)naphthalen-1-ol, have been synthesized and characterized by elemental analysis, IR, UV–Vis, fluorescence spectroscopy and single crystal X-ray diffraction studies. The ligand is so designed that there is no possibility of hydrogen bonding interactions in all the four complexes. However, the C–H⋯π interactions lead to the formation of one-dimensional chain in complex 2 and two-dimensional sheets in the other three complexes. The geometries of all complexes are optimized in the singlet ground states by DFT calculation. Electronic spectra of the complexes are explained using TD DFT calculation.

Three cadmium(II) complexes, [Cd(dmpn)(μ-1,1-N3)2]n (1), [Cd(L1)2Cd(N3)2] (2) and [Cd2(L2)2(Cl)2] (3) {where dmpn is a bidentate chelating ligand N,N-dimethyl-1,3-diaminopropane, HL1 is a tetradentate Schiff base 2-((3-(dimethylamino)propylimino)methyl)-6-methoxyphenol and HL2 is a tridentate Schiff base 2-((2-(diethylamino)ethylimino)methyl)phenol}, were prepared and characterised by elemental analysis, IR, UV–Vis 1H NMR and fluorescence spectroscopy, and single crystal X-ray diffraction studies. Complex 1 is polynuclear with double end-on azide bridges. The hydrogen bonding in complex 1 produces a three-dimensional supramolecular network. Complex 2 is dinuclear and contains octahedral cadmium(II) centres. Complex 3 is also dinuclear, but contains square pyramidal cadmium(II) centres. Intramolecular C–H⋯π interactions are present in complex 2. There is no supramolecular interaction in complex 3. The variation in the denticity of the ligands causes changes in the molecular and crystalline architectures of the complexes. All the three complexes show fluorescence.

A Schiff base ligand (2-{(E)-[2-bromoethyl)imino]methyl}-6-methoxy phenol ( LH ) has been synthesized and characterized by NMR, IR spectroscopy and elemental analysis. The reaction of LH with nickel acetate tetrahydrate results in the formation of a nickel(II) complex ( 1 ). The ligand ( LH ) has been converted into a heterocyclic moiety, 9-methoxy-2,3-dihydro-1,4-benzoxyzepine ( L ) in 1 and coordinated to nickel(II) ion. Ligand substitution reaction of 1 with 3-aminopyridine leads to the formation of 3-aminopyridine derivative of complex 1 , [{3-(NH 2 -Py)} 4 Ni(H 2 O) 2 ]Br 2 ⋅2(CH 2 Cl 2 ) ( 2 ). Complexes 1 and 2 were characterized by using standard analytical techniques and their solid-state structures were confirmed by single crystal X-ray diffraction studies. Complex 1 crystallizes in orthorhombic space group P ccn with cell dimensions of a = 7.8483(10) A, b = 30.662(3) A, c = 9.3872(11) A, Z = 4 and complex 2 crystallizes in orthorhombic space group F ddd with cell dimensions of a = 8.8108(4) A, b = 21.0583(11) A, c = 34.1913(17) A, Z = 8. The optical properties and thermogravimetric analyses of complexes 1 and 2 are also reported.

Two nickel(II) complexes, [Ni(deen)(N3)2]n (1) and [Ni(L)N3] (2), where deen = N,N-diethylethylenediamine, HL = 2-(1-(2-(diethylamino)ethylimino)ethyl)phenol, have been prepared and characterized by elemental analysis, IR and UV–Vis spectroscopy and single crystal X-ray diffraction studies. Complex 1 is polynuclear with alternating double end-on and end-to-end azide bridges, which creates 2D layer with 63-hcb topology. Complex 2 is mononuclear and contains square planar nickel(II). Complex 2 shows significant C–H⋯π interactions and forms a 1D array along with a dimeric unit in the crystal packing.

Two new alternating μ1,1- and μ1,3-azido bridged chains, [Cu(N3)2(mtn)]n (1) and [Ni(N3)2(mtn)]n (2) where mtn = N-methyl-1,3-propanediamine, have been synthesized and characterized by single crystal X-ray diffraction. In both complexes, each metal atom is coordinated to six nitrogen atoms from four azide anions and one N-methyl-1,3-propanediamine molecule in a distorted octahedral geometry. In 1, the basal-apical double μ1,1-azido bridged Cu(ii)-dimers are connected through two asymmetric μ1,3-N3 bridges to form a 1D chain in which one of the azide acts as a μ1,1,3 bridge while the other one is terminal. The structure of 2 is very similar but one of the azide ions acts as μ1,1 and the other as μ1,3 to form an alternating chain. Magnetic data of both compounds were fitted to an alternating ferro/antiferromagnetic chain model (g = 2.120, JF = +15.6 cm(-1), JAF = -2.6 cm(-1) and a paramagnetic impurity of ca. 0.4% for 1 and g = 2.180, JF = +23 cm(-1) and JAF = -33 cm(-1) for 2).

Two copper(II) complexes, [Cu(L)N3]n (1) and [Cu(HL)2](I3)ClO4 (2), where HL = 2-pyridylaldehydesemicarbazone, have been prepared and characterized by elemental analysis, IR and UV–Vis spectroscopy and single crystal X-ray diffraction studies. Complex 1 crystallizes in monoclinic space group P21/a, whereas, complex 2 crystallizes in triclinic space group P-1. Complex 1 is a stair-like coordination polymer with square pyramidal geometry of copper(II), whereas, complex 2 is a mononuclear cationic bis-ligand complex of octahedral copper(II). Lower coordination ability of tri-iodide or perchlorate compared to azide may be related with variations of the structures of the complexes.

Three copper(II) complexes, [Cu(L1)(N3)]n (1), [Cu(L2)(N3)]n.H2O (2) and [Cu(L3)(N3)]n (3) {where HL1 = 2-[(2-dimethylamino-ethylimino)-methyl]-4-nitro-phenol, HL2 = 2-[(2-methylamino-ethylimino)-methyl]-4-nitro-phenol and HL3 = 2-[(2-ethylamino-ethylimino)-methyl]-4-nitro-phenol are tridentate Schiff-base ligands}, were prepared and characterized. Single crystal X-ray diffraction studies confirm that each complex is an end-on azide bridged one-dimensional polymer. All the complexes exhibit a square pyramidal geometry around the copper(II) centre. Weak forces like hydrogen bonding interactions lead to various supramolecular architectures. The copper(II)⋯copper(II) distance is minimized by intra chain hydrogen bonding in complex 3.

Three mononuclear copper(II) complexes, [Cu(L1)(DMF)]ClO4 (1), [Cu(L2)(DMSO)]ClO4 (2) and [CuL3(NCO)] (3) (where HL1 {2-[(2-methylamino-ethylimino)-methyl]-4-nitro-phenol}, HL2 {2-[(2-ethylamino-ethylimino)-methyl]-4-nitro-phenol} and HL3 {2-[(2-(dimethylamino)ethylimino)methyl]-4-nitrophenol} are tridentate Schiff-base ligands), have been synthesized and characterized by elemental analysis, IR and UV–Vis spectroscopy and single-crystal X-ray diffraction studies. All the complexes are square planar. Complex 1 crystallizes in the triclinic space group, P 1 ¯ , with cell dimensions a = 8.0396(2), b = 9.0892(2), c = 12.9977(3) A, α = 85.591(1)°, β = 84.198(1)° and γ = 76.423(1)°, whereas complex 2 crystallizes in the orthorhombic space group, Pbca with cell dimensions a = 8.4615(4), b = 17.2708(11) and c = 25.8517(12) A. Complex 3 crystallizes in the monoclinic space group, P21/n with cell dimensions a = 6.9550(3), b = 13.2257(7), c = 14.7755(6) A and β = 102.697(3)°. Both HL1 and HL2 are capable of forming H bonds due to the presence of H atoms in their amine groups. On the other hand, HL3 cannot form H-bonds. The weak forces like H-bonding, lone pair⋯π and π⋯π interactions lead to various supramolecular architectures in the complexes.

A novel bis(μ-NN'-tetrazolate) bridged centrosymmetric dinuclear nickel(ii) Schiff base complex [Ni2(L)2(PTZ)2]·2H2O·2CH3CN (HL is a tridentate Schiff base, 2-((2-(ethylamino)ethylimino)methyl)-6-methoxyphenol and HPTZ is 5-pyrazinyltetrazole) has been synthesized via [3 + 2] cyclo-addition reaction of 2-cyanopyrazine and sodium azide in presence of nickel(ii) acetate tetrahydrate and HL. The structure of the complex is confirmed by single crystal X-ray diffraction analysis. The combination of H-bonding and C-Hπ interactions creates a 3(6)-hxl topological supramolecular network. The acetonitrile molecules are encapsulated as a hydrophobic guest within the 2D supramolecular network.

Three new copper(II) complexes, [Cu(L)(Cl)]ClO4 (1), [Cu(L)(Br)]ClO4 (2) and [Cu(L)(I)]ClO4 (3), have been prepared from a tetradentate symmetrical Schiff base, N,N′-bis-(1-pyridin-2-yl-ethylidene)-propane-1,3-diamine (L), and characterized by elemental analysis, IR and UV-Vis spectroscopy and single-crystal X-ray diffraction studies. Extended supra-molecular networks were generated through different weak non-covalent forces. Density functional theory (DFT) calculations were employed to estimate the contribution of each interaction in the formation of the assembly using several theoretical models. The interplay between the anion–π and π–π interactions is also analyzed and a mutual reinforcement of both interactions is demonstrated. The assignment of the contribution of each interaction and its mutual influence is certainly important to shed light on the delicate mechanism that governs the molecular recognition and crystal packing.

Four square planar nickel(II) complexes, [Ni(L1)2] (1), [Ni(L2)2] (2), [Ni(L3)(NHEt2)] (3) and [Ni(han)2] (4), where HL1 = 1-(3-hydroxypropyliminomethyl)naphthalene-2-ol, HL2 = 1-(5-hydroxy-3-oxapentyliminomethyl)naphthalene-2-ol, H2L3 = 2-(2-hydroxy-3-methoxybenzylideneamino)phenol and Hhan = 1-hydroxy-2-acetonaphthone, have been prepared and characterized by elemental analyses, IR and UV–Vis spectroscopy and single crystal X-ray diffraction studies. The potential tridentate ONO-donor ligand HL1 and potential tetradentate ONOO-donor ligand HL2 coordinate the nickel(II) only through the amine N and phenolic O to form complexes 1 and 2 respectively, i.e. the ligands act as pendant ligands. On the other hand, the potential tetradentate ONOO-donor Schiff base H2L3 coordinates the nickel(II) only through the amine N atom and two phenolic O atoms to form complex 3, i.e. it also acts as pendant ligand. Complex 4 is formed by the reaction of nickel(II) with 1-hydroxy-2-acetonaphthone. H-bonding, C–H⋯π and π⋯π interactions form supra-molecular assembly.

Three copper(II) complexes [Cu(HL)2(ClO4)]ClO4·H2O (1), [Cu(L)DMF]ClO4 (2) and [CuL(NCO)][Cu2L2(NCO)2] (3) [where HL = 2-[(2-Diethylamino-ethylimino)-methyl]-4-nitro-phenol, a tridentate Schiff-base] have been synthesized and characterized by elemental analysis, IR and UV–Vis spectroscopy and single-crystal X-ray diffraction studies. In complexes 2 and 3, the Schiff base is acting as a tridentate ligand. However, in complex 1, the Schiff base is present in its zwitterionic form. The denticity of the tridentate Schiff base has been modulated by the acidity of counter anions. Complexes 1 and 2 are monomeric. Copper(II) assumes square pyramidal geometry in 1 (Addison parameter (τ) = 0.15) and square planar geometry in 2. The asymmetric unit of complex 3 consists of two crystallographically different double end-on cyanate bridged dimers, containing square pyramidal copper(II) {Addison parameter (τ) = 0.157}. Complexes 1 and 3 crystallize in triclinic space group, P 1 ¯ with cell dimensions a = 11.3479(10), b = 12.5198(9), c = 13.6640(12), α = 94.299(7)°, β = 97.281(7)° and γ = 116.007(6)° (for 1) and a = 11.6149(8), b = 11.8145(9), c = 13.8741(13), α = 65.524(6)°, β = 73.373(6)° and γ = 63.857(5)° (for 3), whereas complex 2 crystallizes in monoclinic space group, P21/c with cell dimensions a = 7.5765(2), b = 19.6005(6), c = 14.5861(4) and β = 102.679(1)° (for 2). The weak forces like lone pair⋯π/π⋯π/anion⋯π interactions lead to various supramolecular architectures.

Three heterometallic nickel(II)–sodium(I) complexes, [Ni(vanen)Na(NO3)] (1), [Ni(vanen)Na(vanen)Ni]BF4 (2) and [Ni(vanen)Na(ClO4)]n (3), have been synthesized by reacting nickel(II) and H2 vanen with sodium(I), varying the reaction conditions and stoichiometry of the reactants [H2vanen = N,N′-ethylene-bis(3-methoxysalicylideneimine)]. All the three complexes have been characterized by X-ray single-crystal diffraction studies. In all the three complexes, nickel(II) is placed in the N2O2 environment and sodium(I) is placed in the O4 compartment of the compartmental Schiff base. In each complex, nickel(II) is square planar. Sodium(I) is trigonal dodecahedral in complex 2, and pentagonal pyramidal both in complexes 1 and 3. The nitrate ion is coordinated to sodium(I) in a chelating bidentate fashion. The sodium(I) in complex 1 shows strong π interaction with the phenyl ring of a second molecule. In complex 3, a carbon atom from an aryl group of a symmetry-related molecule is connected with sodium(I) in η1 fashion to constitute 1D chain. The structure of complex 3 reveals an unprecedented heptadentate coordination mode of the deprotonated Schiff base.

A di-thiocyanato bridged dimeric copper(II) compound has been synthesized using Cu(ClO4)2 and a tridentate Schiff base ligand H2L. During compound formation, ligand H2L has been thiocyanated at the 4 position of the aromatic ring. The X-ray diffraction study confirms the nucleophilic thiocyanation of aryl ring.

Four copper(II) complexes, [Cu(L1)(μ-Cl)]n (1), [Cu2(L2)2(μ-Cl)2] (2), [Cu(L1)(μ1,5-NCNCN)]n (3) and [Cu(L2)(μ1,5-NCNCN)]n (4), where HL1 = 1-[(2-dimethylamino-ethylimino)-methyl]-naphthalen-2-ol and HL2 = 1-[(2-ethylamino-ethylimino)-methyl]-naphthalen-2-ol, acting as tridentate N2O donor ligands, have been prepared and characterized by elemental analysis, IR and UV–Vis spectroscopy and single crystal X-ray diffraction studies. Complexes 1, 3 and 4 show polymeric chain structures, whereas 2 has a double chloride bridged dimeric structure. The existence of C–H⋯π interactions between the dimeric units of 2 gives rise to a 2D supramolecular network. Complex 3 shows a zipper structure through π⋯π interactions between two polymeric chains. Complex 4 shows hydrogen bonding interactions which produces a 2D hydrogen bonded structure and these 2D layers then show interlayer π⋯π interactions.

Four copper(II) complexes [Cu(L1)(dca)]n (1), [Cu(L2)(dca)(H2O)]2 (2), [Cu(L3)(dca)]n (3) and [Cu(L4)(dca)]n (4), where HL1 = 2-[(2-aminoethylimino)methyl]-4-nitrophenol, HL2 = 2-[(2-(methylamino)ethylimino)methyl]-4-nitrophenol, HL3 = 2-[(2-(dimethylamino)ethylimino)methyl]-4-nitrophenol and HL4 = 2-[(2-(diethylamino)ethylimino)methyl]-4-nitrophenol are tridentate Schiff base ligands, were synthesized and characterized by elemental analysis, IR and UV–Vis spectroscopy and single-crystal X-ray diffraction studies. Complex 1 and 4 are 1D helical, complex 2 is dimeric and complex 3 is 1D linear chain. X-ray single crystal structure analyses reveal that in complexes 1, 2 and 4, dicyanamide (dca) anions act as a purely μ-1,5-bridging ligand whereas in case of complex 3, two consecutive dca units serve as 1,3-bridging ligand while the third one exhibits end-to-end 1,5-bridging mode. Copper(II) centers in case of two complexes (1 and 3) exhibit square pyramidal geometry as depicted by Addison parameter (τ) values whereas metal centers of complexes 2 and 4 depict distorted octahedral and square pyramidal geometry respectively. The role of weak forces like lone pair⋯π/π⋯π interactions in influencing the self-assembly process appears to be of importance. Such types of interactions leading to supramolecular network in the four complexes are described here.

Two cobalt(III) complexes, [CoL1(N3)2]ClO4·H2O (1) and [CoL2(N3)2]NO3 (2), where L1 = N,N′-bis-(2-pyridylmethyl)-1,2-ethanediamine, L2 = N,N′-bis-(1-methoxy-1-pyridin-2-yl-methyl)-ethane-1,2-diamine and both ligands are tetradentate N4 donors, have been prepared and characterized by elemental analysis, IR and UV–Vis spectroscopy, cyclic voltammetry and single crystal X-ray diffraction studies. Both compounds assume an asymmetric cis-octahedral (N2/N2) geometry. Complex 1 crystallizes in the orthorhombic space group Pbca with cell dimensions a = 9.7593(2) A, b = 16.8640(3) A, c = 25.8206(5) A, Z = 8, whereas complex 2 crystallizes in the monoclinic space group P21/c with cell dimensions a = 14.437(3) A, b = 15.596(3) A, c = 19.187(3) A, β = 93.642(2), Z = 8. In complex 2, a new bis-hemiaminal ether ligand was found to be “trapped”. Hemiaminal ethers are known to be very unstable intermediates and no crystal structure of any bis-hemiaminal ether has been reported to date. Complex 2 represents a uniquely stable system containing the trapped bis-hemiaminal ether L2.

Tetranuclear [Cu4(L1)2(HL1)2(H2O)](ClO4)2·2H2O (1) and binuclear [Cu2(L2)2]·CH3OH (2) compounds are prepared and the molecular structures elucidated on the basis of X-ray crystallography [H2L1 = 2-[(2-hydroxy-ethylimino)-methyl]-6-methoxy-phenol, H2L2 = 2-[(3-hydroxy-propylimino)-methyl]-6-methoxy-phenol]. Compound 1 is made up of the cation [Cu4(L1)2(HL1)2(H2O)2]2+ and two ClO4− anions which are H-bonded to the cation. The four Cu(II) atoms are not crystallographically equivalent, among then two are in tetragonal [CuNO5] geometries and the rest two are in square pyramidal geometries. The asymmetric unit of compound 2 consists of one neutral [Cu2(L2)2] moiety and a methanol molecule. Each copper atom in compound 2 has a four-coordinate square-planar environment. Compound 1 can be described as an open cage with a [Cu4(μ3-Oal)2(μ2-Oph)2]4+ core (al = alkoxido and ph = phenoxido). Variable temperature solid state magnetic studies between 2–300 K were carried out and the data indicate predominant antiferromagnetic exchange interactions and a spin ground state S = 0. The data were fitted with an average J value model, using the spin Hamiltonian H = −Jav(S1·S2 + S3·S4 + S1·S3 + S2·S4). The best fit was obtained with Jav = −99.0 cm−1. The magnetic properties of compound 2 have also been analyzed and the data show a large antiferromagnetic interaction, in agreement with the [Cu2(μ2-Oal)2]2+ core. The best fit of the data was obtained with J = −891 cm−1 (H = −J S1·S2).

Three heteronuclear Cu(II)/Na(I) complexes, [Cu2(salen)2Na(ClO4)(CH3CN)] (1) [Cu2(vanen)2Na2(μ1,1-NCS)2] (2) and [(Cu)2(L)2(Na)2(μ1,1-CH3CN)(H2O)(ClO4)]ClO4 (3), where H2salen = N,N′-ethylenebis-(salicylideneimine) and H2vanen = N,N′-(1,2-ethylene)-bis(3-methoxysalicylideneimine), have been prepared and characterized by elemental analyses, IR and UV–Vis spectroscopy and single crystal X-ray diffraction studies. Two Cu(II)–salen units are connected by an Na ion in complex 1. Two Cu(II)–vanen–Na(I) moieties are connected by bridging thiocyanate groups in complex 2. A novel end-on bridging asymmetric acetonitrile is observed in complex 3.

Three copper(II) complexes, [Cu2L2(μ1,1-NCO)(NCO)] (1), [Cu2L2(μ1,3-NCS)(NCS)] (2) and [CuL(μ1,5-dca)]n·nH2O (3), where HL = 2-[1-(2-dimethylamino-ethylimino)-ethyl]-phenol, have been prepared and characterized by elemental analysis, IR and UV–Vis spectroscopy, single crystal X-ray diffraction studies and by cyclic voltammetry. Complexes 1 and 3 crystallize in monoclinic space group P21/n and complex 2 in monoclinic P21/c. In complex 1, OCN− shows μ1,1 bridging mode; in complex 2, SCN− shows μ1,3 bridging mode whereas in complex 3, N ( CN ) 2 - shows μ1,5 bridging mode. The tridentate Schiff base ligand reacts with copper(II) to occupy its three equatorial positions. The coordination polyhedra around one of the copper center in compounds 1 and 2 are best described as an elongated (4 + 1) square pyramid, whereas the coordination polyhedra around other copper center is square planer. The copper atom in compound 3 has a slightly distorted square pyramidal environment. Significant C–H/π interactions are observed in both complexes 1 and 2. Complex 3 is an example of MOFs containing penta-cordinated Cu(II) ions linked together by N ( CN ) 2 - to yield 1D infinite P and M-helical chains.

Two isomeric Schiff bases, HL 1 = 1-[(2-dimethylamino-ethylimino)-methyl]-naphthalen-2-ol and HL 2 = 1-[(2-ethylamino-ethylimino)-methyl]-naphthalen-2-ol, have been used to prepare copper(II) complexes in presence of thiocyanate. HL 1 forms a mononuclear complex [Cu(L 1 )NCS] with terminal thiocyanate, whereas the isomeric Schiff base HL 2 , which is capable of hydrogen bonding, gives a dimeric complex, [Cu2 (L 2 ) 2(NCS)2], with double μ-1,1-NCS bridges. Both complexes are characterized by physico-chemical and spectroscopic methods as well as by single crystal X-ray diffraction studies.

Five Fe(III) compounds, [Fe(salophen)(N3)(MeOH)] (1) [Fe(salophen)(NCS)(MeOH)] (2), [Fe(vanophen)(HIm)2]ClO4 (3), [(μ-O){Fe(vanophen)}2]·2H2O (4) and [(μ-O){Fe(naphophen)}2]·2CH2Cl2 (5) where, H2salophen = N,N′-bis(salicylidene)phenylediamine, H2vanophen = N,N′-(1,2-phenylene)-bis(3-methoxysalicylideneimine) and H2naphophen = N,N′-bis(2-hydroxy-1-naphthaldehyde)-1,2-phenylenediimine, have been prepared and characterized by elemental analysis, IR and UV–Vis spectroscopy and single-crystal X-ray diffraction studies. In compounds 1, 2 and 3, Fe(III) has six-coordinated pseudo-octahedral geometry in which the O(1), O(2), N(1) and N(2) atoms of the deprotonated di-Schiff base constitute the equatorial plane. Both in compounds 1 and 2, methanol molecules are present in the fifth coordination sites in apical positions. The sixth coordination sites are occupied by one N atom of an azide in compound 1 and an N atom of thiocyanate in compound 2. In compound 3, both axial positions are occupied by nitrogen atoms from two different imidazole molecules. In both compounds 4 and 5, Fe(III) has a five-coordinated square pyramidal geometry with bridging oxygen atoms in the axial positions.

A copper(II) compound ([LCu(μ-OH)CuL(H2O)]ClO4)n (1) [where HL = 2-[(2-dimethylamino-ethylimino)-methyl]-4-nitro-phenol, is a well known Schiff base], has been synthesized and characterized by elemental analysis, IR and UV–Vis spectroscopy and single-crystal X-ray diffraction studies. The compound features a copper(II) polymeric coordination network composed of binuclear species [LCu(μ-OH)CuL(H2O)]+ as building blocks. It crystallizes in monoclinic space group P21/c with cell dimensions a = 22.1453(9), b = 7.8314(3), c = 18.5626(8) and β=108.509(3). The potentially tridentate Schiff base shows a tetra-dentate bonding mode for the 1st time.

A mono-condensed Schiff base ligand has been prepared as the Cu(II) compound, [Cu2(L1)2(N3)2]·2H2O (1) (HL1 = 1-(N-3-methoxysalicylaldimine)-2-aminoethane), by the reaction of 1,2-diaminoethane, Cu(II) perchlorate and 3-methoxysalicyaldehyde in a 1:1:1 ratio in methanol, followed by the reaction with a large excess of NaN3. In absence of NaN3, a di-condensed compartmental ligand has been trapped as its Cu(II) compound [Cu2(L2)2⊂(H3NC2H4NH3)][{CuL2}2⊂(H3NC2H4NH3)](ClO4)4 (2) (H2L2 = N,N′-ethylenebis(3-methoxysalicylaldimine). Both compounds were characterized by elemental analyses, spectral and electrochemical studies and single crystal X-ray diffraction. In compound 2, Cu(II) has a square planar coordination geometry, while in 1, Cu(II) exhibits a distorted square pyramidal geometry (Addison parameter (τ) = 0.116). [CuL1(py)](ClO4) (3) is produced by following the preparation method of compound 1, but replacing NaN3 with pyridine. Formation of the compounds has been explained by an anion directed template effect.

Three copper(II) compounds, [Cu(L1)(H2O)2]NO3 (1), [Cu(L1)(N3)]·2H2O (2), and [Cu(L2)Cl2] (3), where HL1 = 2-[(pyridine-2-ylmethylene)-amino]-phenol and L2 = (2-methoxy-phenyl)-pyridin-2-ylmethylene-amine are tridentate Schiff-base ligands, have been prepared and characterized by elemental analysis, IR and UV–Vis spectroscopy, Thermo-gravimetric study and single-crystal X-ray diffraction. Compound 1 crystallizes in triclinic space group P1¯ with cell dimensions a = 7.725(5), b = 9.140(5), c = 11.162(5), α = 102.229(5), β = 104.330(5) and γ = 104.710(5), whereas compounds 2 and 3 crystallize in monoclinic space groups P21/c and P21/n respectively with cell dimensions of a = 10.2111(3), b = 6.6366(2), c = 20.8098(5), β = 101.851(2) (for 2) and a = 7.9914(1), b = 18.2591(3), c = 9.5695(2), β = 91.384(1) (for 3). In compound 1, copper(II) center exhibits a distorted square pyramidal geometry while in case of compound 2, copper(II) acquires square planar geometry. The geometry of copper(II) in compound 3 is intermediate between square pyramid and a structure, which is known as ‘inverse square pyramid’. A zipper like infinite chain was formed in compound 2 via hydrogen bonding network between the complex moiety, azide and enclathrated water molecules.

Three heteronuclear Cu(II)/Na(I) compounds, [Cu(vanpn)Na(NO3)(H2O)] (1), [Cu(vanpn)Na(N3)(CH3OH)] (2) and [Cu(vanpn)Na(NCS)(H2O)] (3) where H2vanpn = N,N′-(1,3-propylene)-bis(3-methoxysalicylideneimine), a well known compartmental Schiff base ligand, have been prepared and characterized by elemental analysis, IR and UV–Vis spectroscopy and single crystal X-ray diffraction studies. Compound 1 crystallises in monoclinic space group P21/n, compound 2 in triclinic P 1 ¯ and compound 3 in orthorhombic space group Pbca. In all the compounds, Cu atoms assume distorted square planar geometries whereas Na atoms exhibit distorted octahedral geometry. In compound 1, the nitrate ion is coordinated as a chelating ligand and essentially both the O atoms of the nitrate occupy one axial site. Variation of the counter anions leads to considerable change in the H-bonded supramolecular structures of the compounds. Compound 1 forms a dimer, compound 2 constitutes a chain and compound 3 forms a helix. Electrochemical electron transfer study reveals Cu(II)Cu(I) reduction in acetonitrile solution.

The novel T3(2)4(2)3(2)6(2) tape, constructed by acetate–water hybrid hexamer [(H 2 O) 4 (CH 3 COO) 2 ] 2− , water trimers and tetramer, has been observed for the first time in a heterometallic Schiff base complex host, [Cu(vanpn)Na(CH 3 COO)(H 2 O)]. 2H 2 O, { H 2 v anpn = N , N′ - propylene-bis(3-methoxysalicylideneimine}. The present findings provide insight and serve as a prototype for stabilizing other pure and hybrid water clusters.

Two new double end-to-end azido and thiocyanato bridged copper(II) dimers [Cu2(L1)2(N3)2(ClO4)2] (1) and [Cu2(L2)2(NCS)2](ClO4)2 (2), where L1 (N,N-dimethyl-N′-(1-pyridin-2-yl-ethylidene)-ethane-1,2-diamine) and L2 (N,N-diethyl-N′-(1-pyridin-2-yl-ethylidene)-ethane-1,2-diamine) are tridentate Schiff bases, have been synthesized and their molecular structures have been determined by X-ray crystallography. Copper(II) shows octahedral geometry in 1 and square–pyramidal in 2. The copper(II) in both the compounds are bonded to three nitrogen atoms of the tridentate ligands in mer orientations and the forth coordination sites of basal planes are occupied by the nitrogen atom of azide (in 1) or thiocyanate (in 2). The fifth coordination sites of central copper(II) are occupied by a symmetry related N or S of azide or thiocyanate respectively, thereby creating centrosymmetric dimers. Perchlorate oxygen occupies the sixth coordination site of copper(II) in 1. The octahedral geometry of copper(II) in 1 is facilitated by less steric crowding.

The 1:2 condensation of o-phenelenediamine and o-vanilline yields a compartmental N2O4 ligand N,N′-(1,2-Phenylene)-bis(3-methoxysalicylideneimine) [H2L]. When nickel(II) thiocyanate is added to the methanol solution of H2L, followed by addition of ammonium thiocyanate, an unusual nickel(II) compound, [NH4(NiL)2SCN]·H2O (1), is separated out in which an ammonium ion is sandwiched between two neutral square planner NiL moieties. Hydrogen bonding interactions are observed among the ammonium ion, NiL moieties, the thiocyanate anion and the water of crystallization. The compound is characterized by C, H, N analysis, UV–VIS and IR spectroscopy, room temperature magnetic susceptibility measurement and X-ray crystal diffraction study. The compound crystallizes in monoclinic space group P21/n with a = 13.8636(7) A, b = 14.0267(7) A, c = 22.2715(10) A and β = 94.301(3)°.