Modulation of intermolecular exchange interaction in organic radical based compounds: Magneto-structural analysis of phenol and imidazolium substituted oxoverdazyl radicals

The synthesis of two oxoverdazyls based compounds, the 1,5-dimethyl-3-(2′-hydroxyphenyl)-6-oxoverdazyl 1 and the perchlorate salt of 1,5-dimethyl-3-(2′-imidazolium)-6-oxoverdazyl 2 are reported. The structural analysis of 1 reveals that radicals are closely packed in regular columns by way of π-stacking. In contrast, the packing in 2 is definitely influenced by the protonation state of the radical substituent and shows strong lateral staggering of the organic radicals. The organisation in the solid state strongly influences the intermolecular exchange interaction between π-stacked radicals which goes from J = −113 cm⁻¹ (H = −J∑S_iS_i+1) in 1 to J = −1.0 cm⁻¹ and J′ = −0.67 cm⁻¹ in 2.     

Reactivity of tetracyanoquinodimethane with cobalt(II) chloride and bis(diphylphospino)methane in air

The reactions of CoCl₂·6H₂O, dppm (bis(diphenylphosphino)methane) and TCNQ (7,7,8,8-tetracyanoquinodimethane), with different ratios of the components, provided three new compounds, [Co(dppmdo)₃][TCNQ]₂1 (dppmdo = P,P′-dioxo-bis(diphenylphosphinyl)methane), [Co(dppmdo)₃][(μ-TCNQ)-CoCl₃] 2, and [Co(dppmdo)₃][(μ-DCBE)-CoCl₃] 3 (DCBE = p-dicyanomethyl-benzoic ethyl ester). These products were characterized by IR, UV–Vis and UV–Vis-NIR spectra, X-ray crystallography, magnetic susceptibility measurements and cyclic voltammograms. 1 and 2 reveal low-energy transitions in the near-infrared region, which can be attributed to intra-ligand transitions involving radical anions (TCNQ/TCNQ⁻). It is interesting to note that, except for the redox potentials which are anodically shifted, indicating that it is easier to reduce TCNQ in 1 and 2 than the free TCNQ molecule, the electrochemistry of compounds 1 and 2 resemble that of the independent organic acceptor TCNQ. The magnetic properties suggest that an amount of electron transfer has occurred from the Co^II complex, [Co(dppmdo)₃]²⁺, to the TCNQ⁻ anions in 1; an amount of electron transfer also has occurred from the Co^II cation to the TCNQ⁻ anion via a cyanide-bridge in 2; there is a mixture of spin transition of Co^II ions and antiferromagnetic coupling between Co^II ions in 3.     

Novel nickel(II) and copper(II) complexes with phenoxy-imidazole ligands: Syntheses, crystal structures and norbornene addition polymerization

The novel nickel(II) (1) and copper(II) (2) complexes bearing 2′-(4′,6′-di-tert-butylhydroxy-phenyl)-1,4,5-triphenyl imidazole ligand have been synthesized and characterized. The molecular structure analyses of complexes 1 and 2 indicated that Ni(II) centre in 1 adopts a distorted tetrahedral coordination geometry with a dihedral angle of 85.2° between Ni(1)O(1)N(1) plane and Ni(1)O(1A)N(1A) plane, while the Cu(II) centre in 2 represents a distorted square planar coordination geometry with a cis-N₂O₂ arrangement of the donor atoms, the dihedral angle being 32° between Cu(1)O(1)N(1) plane and Cu(1)O(1A)N(1A) plane. After activation with methylaluminoxane (MAO), both Ni(II) and Cu(II) complexes can be used as catalysts for the addition polymerization of norbornene (NB). The polynorbornenes (PNBs) are produced with very high polymerization activity (10⁸ g PNB mol⁻¹ Ni h⁻¹) for Ni(II) complex and moderate catalytic activity (10⁵ g PNB mol⁻¹ Cu h⁻¹) for Cu(II) complex, respectively. The high molecular weight polynorbornenes (10⁶) are obtained for complexes 1 and 2. Moreover, the distinct effects of polymerization temperature and Al/M ratio on catalytic activities and molecular weights of polymers are discussed.     

Synthesis,structure, optical and magnetic properties of [CrL(X)3], {L = 4′-(2-pyridyl)-2,2′:6′,2″-terpyridine; X = Cl,N3, NCS}

Three complexes of composition [CrL(X)₃], where L = 4′-(2-pyridyl)-2,2′:6′,2″-terpyridine and X = Cl⁻, N₃⁻, NCS⁻ are synthesized. They are characterized by IR, UV–Vis, fluorescence, EPR spectroscopic, and X-ray crystallographic studies. Structural studies reveal that the Cr(III) ion is coordinated by three N atoms of L in a meridional fashion. The three anions occupy the other three coordination sites completing the mer-N₃Cl₃ (1) and mer-N₃N₃ (2 and 3), distorted octahedral geometry. The Cr–N2 has a shorter length than the Cr–N1 and Cr–N3 distances and the order Cr–N(NCS⁻) < Cr–N(N₃⁻) < Cr–Cl is observed. They exhibit some of the d–d transitions in the visible and intra-ligand transitions in the UV regions. The lowest energy d–d transition follows the trend [CrLCl₃] < [CrL(N₃)₃] < [CrL(NCS)₃] consistent with the spectrochemical series. In DMF, they exhibit fluorescence having π → π^∗ character. All the complexes show a rhombic splitting as well as zero-field splitting (zfs) in X-band EPR spectra at 77 K.     

Kinetics and mechanistic studies of the interaction of thiosulfate with cis-diaqua-bis[1-alkyl-2-(arylazo)imidazole]ruthenium(II) complexes

The nucleophilic substitution reaction of S₂O₃²⁻ with [Ru(HaaiR′)₂(OH₂)₂](ClO₄)₂ (1) [HaaiR′ = 1-alkyl-2-(phenylazo)imidazole] and [Ru(ClaaiR′)₂(OH₂)₂](ClO₄)₂ (2) [ClaaiR′ = 1-alkyl-2-(chlorophenylazo)imidazole] [where R′ = Me(a), Et(b) or Bz(c)] in acetonitrile–water (50% v/v) medium to yield Na₂[Ru(HaaiR′)₂(S₂O₃)₂] (3a, 3b or 3c) and Na₂[Ru(ClaaiR′)₂(S₂O₃)₂] (4a, 4b or 4c) has been studied. The products were characterized by microanalytical data and spectroscopic techniques (UV–Vis, NMR and mass spectroscopy). The reaction proceeds in two consecutive steps (A → B → C); each step follows first order kinetics with respect to each complex and S₂O₃²⁻, and the first step second order rate constant (k′₂) is greater than the second step one (k″₂). An increase in the π-acidity of the ligand increases the rate. Thermodynamic parameters, the standard enthalpy of activation (Δ^‡H⁰) and the standard entropy of activation (Δ^‡S⁰), have been calculated for both steps using the Eyring equation from variable temperature kinetic studies. The low Δ^‡H⁰ and large negative Δ^‡S⁰ values indicate an associative mode of activation for both aqua ligand substitution processes.     

Synthesis, photophysical and electrophosphorescent properties of mononuclear Pt(II) complexes with arylamine functionalized cyclometalating ligands

Four cyclometalated Pt(II) complexes, i.e., [(L²)PtCl] (1b), [(L³)PtCl] (1c), [(L²)PtCCC₆H₅] (2b) and [(L³)PtCCC₆H₅] (2c) (HL² = 4-[p-(N-butyl-N-phenyl)anilino]-6-phenyl-2,2′-bipyridine and HL³ = 4-[p-(N,N′-dibutyl-N′-phenyl)phenylene-diamino]-phenyl-6-phenyl-2,2′-bipyridine), have been synthesized and verified by ¹H NMR, ¹³C NMR and X-ray crystallography. Unlike previously reported complexes [(L¹)PtCl] (1a) and [(L¹)PtCCC₆H₅] (2a) (HL¹ = 4,6-diphenyl-2,2′-bipyridine), intense and continuous absorption bands in the region of 300-500 nm with strong metal-to-ligand charge transfer (¹MLCT) (dπ(Pt) → π^∗(L)) transitions (ε ∼ 2 × 10⁴ dm³ mol⁻¹ cm⁻¹) at 449-467 nm were observed in the UV-Vis absorption spectra of complexes 1b, 1c, 2b and 2c. Meanwhile, with the introduction of electron-donating arylamino groups in the ligands of 1a and 2a, complexes 1b and 2b display stronger phosphorescence in CH₂Cl₂ solutions at room temperature with bathochromically shifted emission maxima at 595 and 600 nm, relatively higher quantum yields of 0.11 and 0.26, and much longer lifetimes of 8.4 and 4.5 μs, respectively. An electrochromic film of 1b-based polymer was obtained on Pt or ITO electrode surface, which suggests an efficient oxidative polymerization behavior. An orange multilayer organic light-emitting diode with 1b as phosphorescent dopant was fabricated, achieving a maximum current efficiency of 11.3 cd A⁻¹ and a maximum external efficiency of 5.7%. The luminescent properties of complexes 1c and 2c are dependent on pH value and solvent polarity, which is attributed to the protonation of arylamino units in the C^N^N cyclometalating ligands.     

Syntheses and characterization of η-cyclopentadienyl and η-indenyl ruthenium(II) complexes of arylazoimidazoles: The molecular structure of the complex [(η-C5H5)Ru(PPh3)(C6H5-NN-C3H3N2)]

The complex [(η⁵-C₅H₅)Ru(PPh₃)₂Cl] (1) reacts with several arylazoimidazole (RaaiR′) ligands, viz., 2-(phenylazo)imidazole (Phai-H), 1-methyl-2-(phenylazo)imidazole (Phai-Me), 1-ethyl-2-(phenylazo)imidazole (Phai-Et), 2-(tolylazo)imidazole (Tai-H), 1-methyl-2-(tolylazo)imidazole (Tai-Me) and 1-ethyl-2-(tolylazo)imidazole (Tai-Et), gave complexes of the type [(η⁵-C₅H₅)Ru(PPh₃)(RaaiR′)]⁺ {where R, R′ = H (2), R = H, R′ = CH₃ (3), R = H, R′ = C₂H₅ (4), R = CH₃, R′ = H (5), R, R′ = CH₃ (6), R = CH₃, R′ = C₂H₅ (7)}. The complex [(η⁵-C₉H₇)Ru(PPh₃)₂(CH₃CN)]⁺ (8) undergoes reactions with a series of N,N-donor azo ligands in methanol yielding complexes of the type [(η⁵-C₉H₇) Ru(PPh₃)(RaaiR′)]⁺ {where R, R′ = H (9), R = H, R′ = CH₃ (10), R = CH₃, R′ = H (11), R = CH₃, R′ = C₂H₅ (12)}, respectively. These complexes were characterized by FT IR and FT NMR spectroscopy as well as by analytical data. The molecular structure of the complex [(η⁵-C₅H₅)Ru(PPh₃)(C₆H₅-NN-C₃H₃N₂)]⁺ (2) was established by single crystal X-ray diffraction study.     

Copper(II) complexes of N4 tetradentate ligands with flexible alkyl spacers: Crystal structure,DNA binding and cleavage studies

Mononuclear copper(II) complexes, [Cu L1] (ClO₄)₂ (1), [Cu L2] (ClO₄)₂ (2) and [Cu L3] (ClO₄)₂ (3) with quadridentate Schiff base ligands L1 (N,N′-bis-pyridin-2-ylmethyl-butane-1,4-diimine), L2 (N,N′-bis-pyridin-2-ylmethyl-pentane-1,5-diimine) and L3 (N,N′-bis-pyridin-2-ylmethyl-hexane-1,6-diimine) have been synthesized and characterized. The crystal structure data of 1 reveals the existence of the complex in two different geometries, namely a square pyramid and a distorted octahedron, which eventually leads to the packing of the molecule into helical and anti-parallel structures respectively. Absorption titration studies with calf thymus DNA for all three complexes are suggestive of groove binding with binding constant values for 1, 2 and 3 being 2.6 ± 0.2 × 10⁴ M⁻¹, 11.5 ± 0.2 × 10⁴ M⁻¹ and 1.83 ± 0.2 × 10⁴ M⁻¹ respectively. Control cleavage experiments using pBR 322 plasmid DNA and distamycin suggest minor groove binding for these complexes. In the presence of ascorbic acid, the complexes show efficient DNA cleavage, the order of efficiency being 1 > 2 ≅ 3.     

Oxidative and hydrolytic DNA cleavage by Cu(II) complexes of salicylidene tyrosine schiff base and 1,10 phenanthroline/bipyridine

Ternary Cu(II) complexes [Cu(II)(saltyr)(B)] (1,2), (saltyr = salicylidene tyrosine, B = 1,10 phenanthroline (1) or 2,2′ bipyridine (2)) were synthesized and characterized by various techniques. The complexes exhibit square pyramidal (CuN₃O₂) geometry. CT-DNA binding studies revealed that the complexes show good binding propensity (K_b = 3.47 × 10⁴ M⁻¹ and 3.01 × 10⁴ M⁻¹ for 1 and 2, respectively). The role of these complexes in the oxidative and hydrolytic DNA cleavage was studied. The catalytic ability of 1 and 2 follows the order: 1 > 2. The rate constants for the hydrolysis of phosphodiester bond were determined as 2.80 h⁻¹ and 2.11 h⁻¹ for 1 and 2, respectively. It amounts to (0.58-0.77) × 10⁸ fold rate enhancement compared to non-catalyzed DNA cleavage, which is significant.     

Synthesis, structures and electrochemical properties of ruthenium (II) complexes bearing bidentate 1,8-naphthyridine and terpyridine analogous (N,N,C)-tridentate ligands

1,8-Naphthyridine (napy) and terpyridine-analogous (N,N,C) tridentate ligands coordinated ruthenium (II) complexes, [RuL(napy-κ²N,N′) (dmso)](PF₆)₂ (1: L=L¹=N″-methyl-4′-methylthio-2,2′:6′,4″-terpyridinium, 2: L = L² = N″-methyl-4′-methylthio-2,2′:6′,3″-terpyridinium) were prepared and their chemical and electrochemical properties were characterized. The structure of complex 1 was determined by X-ray crystallographic study, showing that it has a distorted octahedral coordination style. The cyclic voltammogram of 1 in DMF exhibited two reversible ligand-localized redox couples. On the other hand, the CV of 2 shows two irreversible cathodic peaks, due to the Ru-C bond of 2 containing the carbenic character. The IR spectra of 1 in CO₂-saturated CH₃CN showed the formation of Ru-(η¹-CO₂) and Ru-CO complexes under the controlled potential electrolysis of the solution at −1.44 V (vs. Fc/Fc⁺). The electrochemical reduction of CO₂ catalyzed by 1 at −1.54 V (vs. Fc/Fc⁺) in DMF-0.1 M Me₄NBF₄ produced CO with a small amount of HCO₂H.     

Complexes derived from the general copper(II)/maleamic acid/N,N′,N′′-chelate reaction systems: Synthetic,reactivity, structural and spectroscopic studies

The synthetic investigation of the Cu^II/maleamate(−1) ion (HL⁻)/N,N′,N′′-chelate general reaction system has allowed access to compounds [Cu₂(HL)₂(bppy)₂](ClO₄)₂·H₂O (1·H₂O), [Cu(HL)(bppy)(ClO₄)] (2) and [Cu(HL)(terpy)(H₂O)](ClO₄) (4) (bppy = 2,6-bis(pyrazol-1-yl)pyridine, terpy = 2,2′;6′,2′′-terpyridine). In the absence of externally added hydroxides, compound [Cu₂(L′)₂(bppy)₂](ClO₄)₂ (3) was obtained from MeOH solutions; L′⁻ is the monomethyl maleate(−1) ligand which is formed in situ via the Cu^II-assisted HL⁻ → L′⁻ transformation. In the case of tptz-containing (tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine) reaction systems, the Cu^II-assisted hydrolysis of tptz to pyridine-2-carboxamide (L1) afforded complex [Cu(L1)₂(NO₃)₂] (5). The crystal structures of 1–5 are stabilized by intermolecular hydrogen bonding and π–π stacking interactions. Characteristic IR bands of the complexes are discussed in terms of the known structures and the coordination modes of the ligands.     

The (phosphino)tetraphenylborate ligand in ruthenium-arene chemistry

The synthesis of a series of anionic half-sandwich ruthenium-arene complexes [E][RuCl₂(η⁶-p-cymene){PR₂(p-Ph₃BC₆H₄)}] (E = Bu₄N⁺: R = Ph, 1a, ⁱPr, 1b or Cy, 1c; E = bis(triphenylphosphine)iminium or PNP⁺: R = Ph, 1a′, ⁱPr, 1b′ or Cy, 1c′) are reported. X-ray crystallographic studies of 1a′ and 1b′ confirmed the three-legged piano-stool coordination geometry. In solution, complexes 1a-c and 1a′-c′ are proposed to form monomer-dimer equilibria as a result of chloride ligand dissociation. Complexes 1a-c and 1a′-c′ also form the formally neutral zwitterionic complexes [RuCl(L)(η⁶-p-cymene){PR₂(p-Ph₃BC₆H₄)}] (L = pyridine: R = Ph, 2a, ⁱPr, 2b or Cy, 2c; L = MeCN: R = Ph, 3a, ⁱPr, 3b or Cy, 3c) via chloride ligand abstraction using AgNO₃ or MeOTf.     

Thermodynamic and kinetic parameters associated with the fluxional behavior of 2-methyl- and 2,6-dimethyltroponeiron tricarbonyl complexes

The kinetic and thermodynamic parameters for regioisomerisation of 2-methyl- and 2,6-dimethyl-derivatives of tricarbonyl[η⁴-tropone]iron complexes have been studied by ¹H NMR spectrometry over a range of 40 °C. Regioisomerisation of these complexes proceeds by an intramolecular first-order process and results in the almost complete conversion of the less stable complexes (4, 8) to more stable regioisomers (1, 5). The activation energies and half lifes for the conversion (4 → 1) and (8 → 5) were found to be ΔG^#=92 kJ mol⁻¹; τ_1/2=12.8 h, and ΔG^#=107 kJ mol⁻¹; τ_1/2=26.8 h, respectively, at 23 °C. Complex 1 reacts with (1R,2S,5R)-menthol in sulphuric acid solution, followed by neutralisation with sodium carbonate to give a separable mixture of diastereomeric tricarbonyl[(2,3,4,5-η)-(1R^′,2S^′,5R^′)-6-menthyloxy-2-methyltropone]iron complexes, 9 and 10. The corresponding dimethylated complex 5 fails to react under these conditions.     

Synthesis of light-emmting materials bis-[2′-2″-(9H-fluoren-2-yl)-vinyl-8-hydroxyquinoline] zinc(II) and bis-[2′-4″-(4,5-diphenyl-1H-imidazol-2-yl)styryl-8-hydroxyquinoline] zinc(II)

Two novel light-emitting materials bis-[2′-2″-(9H-fluoren-2-yl)-vinyl-8-hydroxyquinoline] zinc(II) (3) and bis-[2′-4″-(4,5-diphenyl-1H-imidazol-2-yl)styryl-8-hydroxyquinoline] zinc(II) (4) containting 8-hydroxyquinoline and fluorene or imidazole moieties have been synthesized. The optical properties of these complexes were influenced by the styryl substituents, and exhibited orange-emission. They have higher fluorescence quantum yields than Alq₃, and good stabilities with thermal decomposition temperatures 395 °C and 435 °C. The single-layer OLED fabricated by 3 emitted lemon-yellow, and exhibited good device performance with a maximum luminance of 489 cd m⁻², and luminance efficiency of up to 0.41 cd A⁻¹. The single-layer OLED fabricated by 4 emitted yellow-green, and exhibited good device performance with a maximum luminance of 323 cd m⁻², and luminance efficiency of up to 0.54 cd A⁻¹.     

On- and off column enantiomerization of 4,4′-bisquinolin-2-ones: A comparison of Auto-, DHPLcy2k and DCXplorer calculated thermodynamic data generated by dynamic high,performance liquid chromatography with theoretically calculated data

Fast semipreparative HPLC enantioseparation of four axially chiral biscarbostyrils (4,4′-bisquinoline-2-ones) using ULMO as a π-acidic Pirkle type chiral stationary phase leads to two racemizing pairs (1,2; k_obs 1.6 × 10⁻⁴ and 3.0 × 10⁻⁴ s⁻¹ at 28 °C) and two stable ones (3,4). 3 was stabilized by a crown ether linkage from pos. 6 to 6′, and 4 had sterically demanding bromo substituents in pos. 3 and 3′. On-column generated temperature-dependent chromatograms of 1 and 2 were fitted with Auto-DHPLCy2k and DCXplorer. For cpd 2 both programs delivered similar ΔG values of 90 and 93 kJ/mol, well comparable with the 99 kJ/mol calculated with the B3LYP/6-31G (d) procedure. At temperatures of high conversion DCXplorer delivered inconsistent series of rate constants for the more tailing and less resolved tetramethoxy derivative 1. We connect this problem with an almost impossible halfwidth calculation of tailing peak pairs which are weakly resolved. However, this problem could be observed only in the case of tetramethoxy derivative 1. Stochastic generated data of Auto-DHPLCy2k could be used at a lower percentage of conversion only while the theoretical plate model did not deliver useful data at temperatures of very low conversion but fitted well high conversion chromatogram series of 1 and 2.     

New interlocked molecules generated from a podand containing urea units and imidazolium salts using an anion template

A podand containing urea units (L) was found to form interlocked structures with 2,5-dihexylamide imidazolium salts (3·X), 2,5-dihexyl imidazolium salts (4·X), and 2,5-dihexyl benzoimidazolium salts (5·X), where X=Cl⁻, Br⁻, and PF₆⁻ using anions as templates. The binding ability of L and guest molecules was evaluated by ¹H NMR titrations in CDCl₃. It was found that L could form complexes with guest molecules in the following order, 3·X > 5·X > 4·X. Stabilities of the complexes also depended on shape of the templated anions: Cl⁻>Br⁻?PF₆⁻. Hydrogen bonding and π-π stacking interactions played an important role in the self-assembling of these interlocked molecules.     

Synthesis,crystal structure and DNA-binding properties of ruthenium(II) polypyridyl complexes with dicationic 2,2′-dipyridyl derivatives as ligands

New Ru(II) complexes with dicationic ligand, [Ru(phen)₂L¹]⁴⁺(1) and [Ru(phen)₂L²]⁴⁺(2) (phen = 1,10-phenanthroline; L: L¹ = 5,5′-di(1-(triethylammonio)methyl)-2,2′-dipyridyl cation; L² = 5,5′-di(1-(tributylammonio)methyl)-2,2′-dipyridyl cation) have been synthesized and structurally characterized. The interaction of these complexes with calf thymus DNA (CT-DNA) has been investigated. The intrinsic binding constants (K_b: 1, 7.73 × 10⁴ M⁻¹; 2, 2.50 × 10⁴ M⁻¹) determined by absorption spectral titrations of these complexes with CT-DNA indicate the DNA-binding affinity of 1 is stronger than that of 2. Both complexes can display luminescence either alone in aqueous solution or in the presence of DNA. Equilibrium dialysis experiments monitored by CD spectroscopy reveal the preferential binding of the Δ-enantiomer to the right-handed CT-DNA. DNA-viscosity studies suggest that the binding modes are different, 1 may partially intercalate between DNA base-pairs while 2 most likely interact with DNA in an electrostatic binding mode.     

Helices of ruthenium complexes involving pyridyl-azine ligands: synthesis, spectral and structural aspects

New cationic complexes [Ru(η⁵-C₅H₅)(EPh₃)(L)]BF₄ [L = pyridine-2-carbaldehyde azine (paa); E = P, 1; E = As, 2; E = Sb, 3] and κ¹ bonded dppm complexes [Ru(η⁵-C₅H₅)(κ¹-dppm)(L)]BF₄ [L = paa 4; L = p-phenylene-bis(picoline)aldimine (pbp) 5] containing both group V donor and pyridyl-azine ligand are reported. The complexes were fully characterized by analytical and spectral studies. ³¹P NMR spectral studies suggested coordination of dppm in the complexes 4 and 5 in κ¹-manner, which was further, confirmed by structural studies on the representative complex 4. Weak interaction studies revealed that inter- and intramolecular C-H?X (X = O, F, Cl, π) and π-π interactions in the complexes 1 and 4 lead to helical structures.     

Syntheses and X-ray crystallographic studies of {[Ni(en)2(pot)2]0.5CHCl3} and [Ni(en)2](3-pytol)2

Two novel Ni(II) complexes {[Ni(en)₂(pot)₂]0.5CHCl₃} (3) {pot = 5-phenyl-1,3,4-oxadiazole-2-thione} (1) and [Ni(en)₂](3-pytol)₂ (4) {3-pytol = 5-(3-pyridyl)-1,3,4-oxadiazole-2-thiol} (2) have been synthesized using en as coligand. The metal complexes have been characterized by physical and analytical techniques and also by single crystal X-ray studies. The complexes 3 and 4 crystallize in monoclinic system with space group P21/a and P121/c, respectively. The complex 3 has a slightly distorted octahedral geometry with trans (pot)⁻ ligands while 4 has a square planar geometry around the centrosymmetric Ni(II) center with ionically linked trans (3-pytol)⁻ ligands. The π?π (face to face) interaction plays an important role along with hydrogen bondings to form supramolecular architecture in both complexes.