Assembly of novel phenanthroline-based cobalt(II) coordination polymers by selecting dicarboxylate ligands with different spacer length: From 1-D chain to 3-D interpenetrated framework

Three novel Co^II coordination polymers [Co(Dpq)₂(1,4-NDC)_0.5] · (1,4-HNDC) (1), [Co(Dpq)(2,6-NDC)] (2), and [Co₂(Dpq)₂(BPEA)₄(H₂O)] · H₂O (3) have been obtained from hydrothermal reaction of cobalt nitrate with the mixed ligands dipyrido[3,2-d:2′,3′-f]quinoxaline (Dpq) and three dicarboxylate ligands with different spacer length [1,4-naphthalene-dicarboxylic acid (1,4-H₂NDC), 2,6-naphthalene-dicarboxylic acid (2,6-H₂NDC) and biphenylethene-4,4′-dicarboxylic acid (BPEA)]. All these complexes are fully structurally characterized by elemental analysis, IR, and single-crystal X-ray diffraction analysis. Single-crystal X-ray analysis reveal that complex 1 is infinite one-dimensional (1-D) chains bridged by 1,4-NDC ligands, which are extended into a two-dimensional (2-D) supramolecular network by π-π interactions between the Dpq molecules. Complex 2 is a distorted three-dimensional (3-D) PtS network constructed from infinite Co-O-C rod units. Complex 3 has a 5-fold interpenetrated 3-D structure with diamondoid topology based on dinuclear [Co₂(CO₂)₂(μ₂-OH₂)N₄O₂] units and BPEA molecules. The different structures of complexes 1-3 illustrate the influence of the length of dicarboxylate ligands on the self-assembly of polymeric coordination architectures. In addition, the thermal properties of complexes 1-3 and fluorescent properties of complexes 2 and 3 have been investigated in the solid state.     

Hydrothermal synthesis, crystal structures and fluorescence properties of three novel frameworks constructed with mixed ligands of isophthalic acid (1,3-BDC) and 2,3-di-2-pyridylquinoxaline (Dpdq): [M(1,3-BDC)(Dpdq)(H2O)m] · nH2O (M = Co, Cd or Zn)

Three novel metal-organic frameworks [M(1,3-BDC)(Dpdq)(H₂O)_m] · nH₂O, (M = Co^II (1), Cd^II (2) or Zn^II (3); m = 0, 1; n = 0, 1, 2, respectively) have been obtained from hydrothermal reactions of three different metal(II) nitrates with the same mixed ligands [isophthalic acid (1,3-BDC) and 2,3-di-2-pyridylquinoxaline (Dpdq)], and structurally characterized by elemental analyses, IR spectroscopy, and single-crystal X-ray diffraction analyses. Single-crystal X-ray analyses show that each pair of metal ions are bridged by various coordination modes of 1,3-BDC ligands to form left- and right-handed helical chains in 1, linear chains in 2, and double chains in 3, respectively. N-containing flexible ligand Dpdq takes a chelating coordination mode acting as terminal ligand. In the compound 1, adjacent left- and right-handed helical chains are packed through hydrogen bonds to form a two-dimensional (2-D) structure. In the compounds 2 and 3, adjacent chains are further linked by hydrogen bonds and/or π-π stacking interactions to form a three-dimensional (3-D) distorted hexagon meshes supramolecular framework for 2 and a ZnS-related three-dimensional (3-D) topology for 3, respectively. The different structures of compounds 1-3 illustrate that the influence of the metal ions in the self-assembly of polymeric coordination architectures. In addition, compounds 2 and 3 exhibit blue emission in the solid state at room temperature.     

Interaction of copper(II) and palladium(II) with linked 2,2′-dipyridylamine derivatives: Synthetic and structural studies

Interaction of copper(II) salts with 2,2′-dipyridylamine (1), N-cyclohexylmethyl-2,2′-dipyridylamine (2), di-2-pyridylaminomethylbenzene (3), 1,2-bis(di-2-pyridylaminomethyl)-benzene (4), 1,3-bis(di-2-pyridylaminomethyl)benzene (5), 1,4-bis(di-2-pyridylaminomethyl)benzene (6), 1,3,5-tris(di-2-pyridylaminomethyl)benzene (7) and 1,2,4,5-tetrakis(di-2-pyridylaminomethyl)benzene (8) has yielded the following complexes: [Cu(2)(μ-Cl)Cl]₂, [Cu(3)(μ-Cl)Cl]₂ · H₂O, [Cu₂(4)(NO₃)₄], [Cu₂(5)(NO₃)₄] · 2CH₃OH, [Cu₂(6)(CH₃OH)₂(NO₃)₄], [Cu₄(8)](NO₃)₄] · 4H₂O while complexation of palladium(II) with 1, 4, 5 and 6 gave [Pd(1)₂](PF₆)₂ · 2CH₃OH, [Pd₂(4)Cl₄], [Pd₂(4)(OAc)₄], [Pd₂(5)Cl₄], [Pd₂(6)Cl₄] and [Pd₂(6)(OAc)₄] · CH₂Cl₂, respectively. X-ray structures of [Cu(2)(μ-Cl)Cl]₂, [Cu(3)(μ-Cl)Cl]₂ · 2C₂H₅OH, [Cu₂(6)(CH₃OH)₂(NO₃)₄], [Pd(1)₂](PF₆)₂ · 2CH₃OH, [Pd₂(4)(OAc)₄] · 4H₂O and [Pd₂(6)(OAc)₄] · 2CH₂Cl₂ are reported. In part, the inherent flexibility of the respective ligands has resulted in the adoption of a diverse range of coordination geometries and lattice arrangements, with the structures of [Pd₂(4)(OAc)₄] · 4H₂O and [Pd₂(6)(OAc)₄] · 2CH₂Cl₂, incorporating the isomeric ligands 4 and 6, showing some common features. Liquid–liquid (H₂O/CHCl₃) extraction experiments involving copper(II) and 1–3, 5, 7and 8 show that the degree of extraction depends markedly on the number of dpa-subunits (and concomitant lipophilicity) of the ligand employed with the tetrakis-dpa derivative 8 acting as the most efficient extractant of the six ligand systems investigated.     

Synthesis,structures and NLO properties of five non-centrosymmetric coordination compounds from the copper(II)/dps system (dps = 4,4′-dipyridyl sulfide)

The formation, crystal structure and properties of five copper(II) coordination compounds with the angular ligand, 4,4′-dipyridyl sulfide (dps) are described, {[Cu₃(μ-dps)₄(μ-SO₄)₂(SO₄)(H₂O)₅] · 10H₂O}_∞ (1 · 10H₂O), [Cu(dps)₄(H₂O)₂] · (ClO₄)₂ · H₂O (2 · H₂O), {[Cu(μ-dps)₂(DMF)₂](ClO₄)₂}_∞ (3), {[Cu(μ-dps)₂(H₂O)₂] · (NO₃)₂ · 2H₂O}_∞ (4 · 2H₂O) and {[Cu₃(μ-dps)₆(DMF)₂(H₂O)₄] · (NO₃)₆ · (DMF) · 6H₂O}_∞ (5 · DMF · 6H₂O). The topological architectures of all these coordination compounds are strongly dependent on the counteranions, with the aid of guest solvents, and include a chiral 3D non-interpenetrated structure for 1, an acentric mononuclear structure for 2, acentric 2D undulating networks for 3 and 5, and a chiral 1D double-stranded chain for 4. In particular, all these acentric or chiral coordination architectures are generated from an achiral ligand as a building unit, and their second-order non-linear optical (NLO) properties are also studied in this paper.     

Three new 3-D inorganic-organic coordination polymers constructed from polyoxovanadate-based heterometallic network and flexible bis(imidazole) ligand: Syntheses, structures and properties

Three new 3-D inorganic-organic polyoxovanadate-based coordination polymers [M₂(bbi)(V₂O₆)₂(H₂O)₂] [M = Co (1), Mn (2)] and [Ni₂(bbi)₃V₄O₁₂]·4H₂O (3) (bbi = 1,1-(1,4-butanediyl)bis(imidazole)) have been synthesized under hydrothermal condition and characterized by elemental analyses, IR spectra, TG and single crystal X-ray diffraction. The 3-D networks of compounds 1 and 2 are constructed from neutral {M₂V₄O₁₂} [M = Co (1), Mn (2)] layers that are pillared via the coordination of organic ligands bbi to M sites. Compound 3 is a 3-D eight-connected network, in which each binuclear [Ni₂O₄N₆] node linked with other eight adjacent nodes through two {V₄O₁₂}⁴⁻ clusters and six bbi ligands. The electrochemical behaviors of 1-3 modified carbon paste electrodes (1-CPE, 2-CPE and 3-CPE) in 1 M H₂SO₄ aqueous solution have been reported.     

Novel dinuclear and polynuclear copper(II)-pyrazine-2,3-dicarboxylate supramolecular complexes with 1,3-propanediamine, N,N,N′,N′-tetramethylethylenediamine and 2,2′-bipyridine

Three novel Cu(II)-pyrazine-2,3-dicarboxylate complexes with 1,3-propanediamine (pen), [Cu₂(μ-pzdc)₂(pen)₂] · 2H₂O (1), N,N,N′,N′-tetramethylethylenediamine (tmen), {[Cu(μ-pzdc)(tmen)] · H₂O}_n(2), and 2,2′-bipyridine (bipy), {[Cu(μ-pzdc)(bipy)]·H₂O}_n(3) have been synthesized and characterized by means of elemental and thermal analyses, magnetic susceptibilities, IR and UV/vis spectroscopic studies. The molecular structures of dinuclear (1) and polynuclear (2 and 3) complexes have been determined by the single crystal X-ray diffraction technique. The pyrazine-2,3-dicarboxylate acts as a bridging ligand through oxygen atom of carboxylate group and N atom of pyrazine ring and one oxygen atom of neighboring carboxylate. It links the Cu(II) ions to generate a distorted square pyramidal geometry forming a one-dimensional (1D) chain. Adjacent chains of 1 and 2 are then mutually linked via hydrogen bonding interactions, which are further assembled to form a two and three-dimensional network, respectively. The chains of complex 3 are further constructed to form three-dimensional framework by hydrogen bonding, C–H?π and ring?ring stacking interactions. In the complexes, Cu(II) ions have distorted square pyramidal geometry. Thermal analyses properties and thermal decomposition mechanism of complexes have been investigated by using thermal analyses techniques (TG, DTG and DTA).     

R-phenyldicarboxyl (R = H, NO2 and COOH) modular effect on Ni(II) coordination polymers incorporated with a versatile connector 1H-3-(3-pyridyl)-5-(4-pyridyl)-1,2,4-triazole

Based on the versatile ligand 1H-3-(3-pyridyl)-5-(4-pyridyl)-1,2,4-triazole (3,4′-Hbpt) (1), a series of coordination compounds [Ni(3,4′-Hbpt)(ip)] (2), [Ni(3,4′-Hbpt)₂(tp)(H₂O)₂] (3), [Ni₂(3,4′-Hbpt)(5-NO₂-ip)₂(H₂O)₄] (4) and [Ni(3,4′-Hbpt)(pm)_0.5(H₂O)₃]·2H₂O (5) have been hydrothermally constructed through R-phenyldicarboxyl (R = H, NO₂ and COOH) intervention effect (ip = isophthalic anion, tp = terephthalic anion, 5-NO₂-ip = 5-NO₂-isophthalic anion, pm = pyromellitic anion). Structural analysis reveals that 3,4′-Hbpt adopts μ-N_py, N_py coordination modes in two typical conformations in these target coordination compounds. In cooperation with the auxiliary ligands benzenedicarboxylate connectors, a variety of Ni(II) coordination networks such as 2-D layer with (4, 4) topology (2) 1-D chain (3), honeycomb (4) and 2-D helical chains (5) have been assembled. Theoretical calculation based on density functional theory (DFT) for ligand (1) is also employed to explicate the stability of the different conformations. Moreover, thermal stability of these crystalline materials is explored by TG-DTG.     

Syntheses, crystal structures and magnetic properties of two dicopper(II) complexes and a zigzag 1-D Cu(II) complex of a bidentate pyridyl-pyrazole ligand

Two new dinuclear copper compounds, [Cu₂(pypz)₂(N₃)₂(NO₃)₂] (1) and [Cu₂(pypz)₂(OH)₂(NO₃)₂] (2), and one 1-D polymeric Cu(II) complex, [Cu(pypz)(dca)₃]_n (3) [‘pypz’ = (3,5dimethyl-1-(2′-pyridyl)pyrazole) and dca = (dicyanamide)], have been synthesized and characterized crystallographically and spectroscopically. Complex 1 is pseudo-octahedral, adjacent Cu atoms are connected by a pair of μ(1,1) azido groups and the structure is stabilized by π-π interactions between two pyridyl moieties from two different neighboring complex molecules. Complexes 2 and 3 are square pyramidal. The hydroxo bridged complex 2 is further stabilized through H-bonding. The 1-D polymeric chain of 3 is bridged by an end-to-end dicyanamide bridge and it propagates along the crystallographic b axis, whilst the polymer chains are stacked one upon another along the crystallographic c axis. Low temperature magnetic measurement shows that complexes 1 and 2 are ferromagnetic (J values are 30.81 and 14.79 cm⁻¹, respectively), whereas due to larger Cu-Cu distances, complex 3 shows weak ferromagnetism.     

Copper(II) complexes of tetradentate N2S2 donor sets: Synthesis,crystal structure characterization and reactivity

Two mononuclear and one dinuclear copper(II) complexes, containing neutral tetradentate NSSN type ligands, of formulation [Cu^II(L¹)Cl]ClO₄ (1), [Cu^II(L²)Cl]ClO₄ (2) and [Cu^II₂(L³)₂Cl₂](ClO₄)₂ (3) were synthesized and isolated in pure form [where L¹ = 1,2-bis(2-pyridylmethylthio)ethane, L² = 1,3-bis(2-pyridylmethylthio)propane and L³ = 1,4-bis(2-pyridylmethylthio)butane]. All these green colored copper(II) complexes were characterized by physicochemical and spectroscopic methods. The dinuclear copper(II) complex 3 changed to a colorless dinuclear copper(I) species of formula [Cu^I₂(L³)₂](ClO₄)₂,0.5H₂O (4) in dimethylformamide even in the presence of air at ambient temperature, while complexes 1 and 2 showed no change under similar conditions. The solid-state structures of complexes 1, 2 and 4 were established by X-ray crystallography. The geometry about the copper in complexes 1 and 2 is trigonal bipyramidal whereas the coordination environment about the copper(I) in dinuclear complex 4 is distorted tetrahedral.     

Metal-directed supramolecular assembly of metal(II) benzoates (M = Co,Ni, Cu,Zn, Mn,and Cd) with 4,4′-bipyridine: Effects of metal coordination modes and novel catalytic activities

Six polymeric metal(II)-benzoate complexes of formula [Co₂(O₂CPh)₄(4,4′-bpy)₂]_n (1-Co), [Ni(O₂CPh)₄(H₂O)₂(4,4′-bpy)]_n (2-Ni), [Cu₂(O₂CPh)₄(4,4′-bpy)]_n (3-Cu), [Zn₂(O₂CPh)₂(OH)₂(4,4′-bpy)₂]_n (4-Zn), [Zn₃(O₂CPh)₄(μ-OH)₂(4,4′-bpy)₂]_n (5-Zn), and [Cd₂(O₂CPh)₄(4,4′-bpy)₂]_n (6-Cd) have been synthesized and characterized (4,4′-bpy = 4,4′-bipyridine). 1-Co and 6-Cd show ladder-type double chains, 2-Ni does a helical structure, 3-Cu does a one-dimensional chain containing paddle-wheel units, 4-Zn does a zigzag chain, and 5-Zn does two-dimensional sheets. Since different structures provide different coordination geometry of each metal ion, it is clear that selection of appropriate metal ions can control the coordination geometry of each metal ion to form different crystal structures. Reactivity study of the compounds 1–7 for the transesterification of a variety of esters has shown that 4-Zn and 5-Zn are very efficient and the best among them. The catalyst 6-Cd containing Cd ion, well known as an inert metal ion for the ligand substitution, also catalyzed efficiently the transesterification of a variety of esters, and its reactivity is comparable to 4-Zn and 5-Zn. Moreover, the redox-active metal-containing polymers, 1-Co, 3-Cu, and 7-Mn, have shown efficient catalytic reactivities for the transesterification reactions, while 2-Ni has displayed a very slow conversion. The reactivities of the compounds used in this study are in the order of 5-Zn > 4-Zn > 6-Cd > 7-Mn ∼ 3-Cu > 1-Co > 2-Ni, indicating that the non-redox metal-containing compounds (5-Zn, 4-Zn, and 6-Cd) show better activity than the redox-active metal-containing compounds (7-Mn, 3-Cu, 1-Co, and 2-Ni). These results suggest that it is possible to tune the catalytic activities by changing from Zn to those metals such as Cd, a kinetically inert metal, or Cu, Mn, and Co, the redox-active metals.     

An unprecedented extended architecture constructed from a 2-D interpenetrating cationic coordination framework templated by SiW12O40 anion

A novel inorganic-organic hybrid compound based on polyoxometalates (POMs) and organic ligand formulated as [Cu₂(bpp)₄(H₂O)₂](SiW₁₂O₄₀)∼6H₂O (1) [bpp=1,3-bis(4-pyridyl)propane], was hydrothermally synthesized and structurally characterized by elemental analysis, single-crystal X-ray diffraction analysis, IR, TG, and cyclic voltammetry. Crystal data for 1: Orthorhombic, Pbcn, a=23.0085(19) Å, b=14.6379(12) Å, c=23.6226(19) Å, V=7956.0(11) Å³, Z=4, Dc=3.315 g cm^-3, and R(final)=0.0826. X-ray diffraction study reveals that compound 1 was the first interpenetrating network of 2-D metal-organic cationic coordination framework [Cu₂(bpp)₄(H₂O)₂]_n⁴ⁿ⁺, in which Keggin-type anions SiW₁₂O₄₀^4- has been used as a non-coordinating anionic template. The electrochemical property of 1-bulk modified carbon paste electrode (1-CPE) has been studied, and the results indicate that 1-CPE has good electrocatalytic activities toward the reduction of nitrite in 1 M H₂SO₄ aqueous solution.     

Structural diversity in Cu(II), Cd(II) and Hg(II) coordination complexes with the rigid N,N′-bis(2/3-aryl)-1,4-benzenedicarboxamide ligand

The syntheses and structures of a series of metal complexes, namely Cu₂Cl₄(L¹)(DMSO)₂·2DMSO (L¹ = N,N′-bis(2-pyridinyl)-1,4-benzenedicarboxamide), 1; {[Cu(L²)_1.5(DMF)₂][ClO₄]₂·3DMF}_∞ (L² = N,N′-bis(3-pyridinyl)-1,4-benzenedicarboxamide), 2; {[Cd(NO₃)₂(L³)]·2DMF}_∞ (L³ = N,N′-bis-(2-pyrimidinyl)-1,4-benzenedicarboxamide), 3; {[HgBr₂(L³)]·H₂O}_∞, 4, and {[Na(L³)₂][Hg₂X₅]·2DMF}_∞ (X = Br, 5; I, 6) are reported. All the complexes have been characterized by elemental analysis, IR spectra and single crystal X-ray diffraction. Complex 1 is dinuclear and the molecules are interlinked through S?S interactions. In 2, the Cu(II) ions are linked through the L² ligands to form 1-D ladder-like chains with 60-membered metallocycles, whereas complexes 3 and 4 form 1-D zigzag chains. In complexes 5 and 6, the Na(I) ions are linked by the L³ ligands to form 2-D layer structures in which the [Hg₂X₅]⁻ anions are in the cavities. The L² ligand acts only as a bridging ligand, while L¹ and L³ show both chelating and bridging bonding modes. The L¹ ligand in 1 adopts a trans-anti conformation and the L² ligand in 2 adopts both the cis-syn and trans-anti conformations, whereas the L³ ligands in 3–6 adopt the trans conformation.     

Supramolecular assembly of new heteropolymetalic molecules based on tetraiminodiphenolate macrocycle and hexacyanometallate anions: Magnetostructural and spectroscopic properties

Herein we report on the synthesis, single crystal X-ray structure, spectroscopic and magnetic properties of [{Cu₂(tidf)(H₂O)}₂(μ-CN)₂Fe(CN)₄]·6H₂O (1), [Cu₂(tidf)(H₂O)₂][Ni(CN)₄] (2) and [Cu₂(tidf)(H₂O)₂][Fe(CN)₅NO]·H₂O (3) (tidf = a Robson type macrocyclic ligand obtained on condensation of 2,6-diformyl-4-methylphenol and 1,3-diaminopropane). Complex (1) is pentanuclear; two paramagnetic dicopper(II) units are linked by a hexacyanoferrate(II) ion through two cyano-bridges. All compounds exhibit extensive, three-dimensional, supramolecular structures supported by classic hydrogen bonding between the coordinated aqua ligands, water molecules and cyano groups. Magnetism as a function of the temperature of complexes 1-3 is consistent with a strong antiferromagnetism with exchange parameters 2J estimated −783(29), −913(2), −905(1), respectively.     

Heterocyclic thioamides of copper(I): Synthesis and crystal structures of copper complexes with 1,3-imidazoline-2-thiones in the presence of triphenyl phosphine

Reaction of copper(I) chloride with 1,3-imidazoline-2-thione (imzSH) in the presence of Ph₃P in 1:2:2 or 1:1:2 (M:L:PPh₃) molar ratios yielded a compound of unusual composition, [Cu₂(imzSH)(PPh₃)₄Cl₂] · CH₃OH (1), whose X-ray crystallography has shown that its crystals consist of four coordinated [CuCl(1κS-imzSH)(PPh₃)₂] (1a), and three coordinated [Cu(PPh₃)₂Cl] (1b) independent molecules in the same unit cell. In contrast, crystals of complexes of copper(I) bromide/iodide are formed by single molecules of [CuBr(1κS-imzSH)(PPh₃)₂] · H₂O (2) and [CuI(1κS-imzSH)(PPh₃)₂] (3), respectively, similar to molecule 1a. The related ligand, 1,3-benzimidazoline-2-thione (bzimSH) formed a complex [CuBr(1κS-bzimSH)(PPh₃)₂] · CH₃COCH₃ (4), similar to 2. The formation of 1a and 1b has been also revealed by NMR spectroscopy. The NMR spectra of 2–4 also showed weak signals indicating formation of compounds similar to 1b. It reveals that the lability of the Cu–S bond varies in the order: Cl ? Br ∼ I. Weak interactions {e.g. C–H?π electrons of ring, –NH?halogens/oxygen, C–H?halogens/oxygen, π?π (between rings)} have played an important role in building 2D chains of complexes 1–4.     

Cu acetate complexes involving N,N,O donor Schiff base ligands: Mono-atomic oxygen bridged dimers and alternating chains of the dimers and Cu2(OAc)4

Two tridentate N,N,O donor Schiff bases, HL¹ (4-(2-ethylamino-ethylimino)-pentan-2-one) and HL² (3-(2-amino-propylimino)-1-phenyl-butan-1-one) on reaction with Cu^II acetate in presence of triethyl amine yielded two basal-apical, mono-atomic acetate oxygen-bridging dimeric copper(II) complexes, [Cu₂L¹₂(OAc)₂] (1), [Cu₂L²₂(OAc)₂] (2). Whereas two other similar tridentate ligands HL³ (4-(2-amino-propylimino)-pentane-2-one) and HL⁴ (3-(2-amino-ethylimino)-1-phenyl-butan-1-one) under the same conditions produced a mixture of the corresponding dimers and a one-dimensional alternating chain of the dimer and copper acetate moiety, [Cu₄L³₂(OAc)₆]_n (3) and [Cu₄L⁴₂(OAc)₆]_n (4), formed by a very rare μ₃ bridging mode of the acetate ion. All four complexes (1–4) have been characterized by X-ray crystallography. The isotropic Hamiltonian, H = −JS₁S₂ has been used to interpret the magnetic data. Magnetic measurements of 1 and 2 in the temperature range 2–300 K reveal a very weak antiferromagnetic coupling for both complexes (J = −0.56 and −1.19 cm⁻¹ for 1 and 2, respectively).     

Self-assembled multilayer films of poor water-soluble copper(II) complexes constructed from dipyrido[3,2-d:2′,3′-f]quinoxaline (Dpq) ligand as well as their fluorescent properties

New multilayer films were prepared by alternating adsorption of poly(sodium 4-styrenesulfonate) (PSS) and a new complex of [Cu₂(Dpq)₂(Ac)₂(H₂O)₂] (ClO₄)₂·H₂O (1) (Dpq=dipyrido[3,2-d:2′,3′-f]quinoxaline, Ac=acetate) or a related complex [Cu(Dpq)₂(H₂O)] (ClO₄)₂·H₂O (1a) by electrostatic layer-by-layer self-assembly technique, respectively. Compounds 1 and 1a have been synthesized and structurally characterized by elemental analyses, IR spectroscopy, and single-crystal X-ray diffraction analyses. Single-crystal X-ray analyses show that complexes 1 and 1a possess a dinuclear and a mononuclear structure, respectively, which are further extended into layered frameworks by π-π stacking and hydrogen-bonding interactions. The multilayer films were characterized by UV-vis spectroscopy, fluorescence spectroscopy, small-angle X-ray reflectivity measurements, and atomic force microscopy (AFM) imaging. UV spectroscopy shows that the deposition process is regular and highly reproducible from layer to layer. AFM image indicates that the film surface is uniform and smooth. The fluorescent properties of the films were studied and the results showed that the forming condition of the films had great influence on their properties.     

Structural,spectroscopic and redox properties of transition metal complexes of dipyrido[3,2-f:2′,3′-h]-quinoxaline (dpq)

The chemistry of first row transition metal complexes obtained from the ligand dipyrido[3,2-f:2′,3′-h]-quinoxaline (dpq) have been reported. The reaction between Cu(ClO₄)₂ · 6H₂O with dpq under different reaction conditions led to the isolation of three polymorphic copper(II) complexes [Cu(dpq)₂(H₂O)](ClO₄)₂ · H₂O (2), [Cu(dpq)₂(ClO₄)](ClO₄) (3) and [{Cu(dpq)₂(H₂O)}{Cu(dpq)₂(ClO₄)}](ClO₄)₃ (4). The bluish-green compound 2, obtained by reacting Cu(ClO₄)₂ · 6H₂O with dpq in methanol, has a distorted trigonal bipyramidal structure with τ = 0.55. The reaction between Cu(ClO₄)₂ · 6H₂O and dpq in dry acetonitrile produced the blue compound 3 in which the copper(II) centre has a distorted square planar geometry. When the condensation reaction between 1,10-phenanthroline-5,6-dione and 1,2-diaminoethane was carried out in the presence of Cu(ClO₄)₂ · 6H₂O in methanol, the green copper(II) complex 4 was isolated along with 1. The structure determination of 4 has established the presence of two different complex cations in the asymmetric unit and they are considered as co-crystals. In the zinc(II) compound [Zn(dpq)₂(ClO₄)₂] (5), the two perchlorates are unidentately coordinated to the metal centre, providing a distorted octahedral geometry. The quinoxaline ring in 5 is involved in intermolecular π–π interactions, leading to the generation of a sinusoidal chain. The proton NMR spectra, especially those of the paramagnetic complexes [Ni(dpq)₃](ClO₄)₂ (6) and [Co(dpq)₃](ClO₄)₂ (7), have been studied in detail. The electronic absorption spectra and the redox behaviour of the copper(I), copper(II), cobalt(II) and cobalt(III) complexes have been studied. The three copper(II) compounds 2–4 show identical absorption spectra and redox properties when measured in acetonitrile, although in nitromethane they show small but definite differences in their spectral and redox features.     

Copper benzenedicarboxylate coordination polymers incorporating a long-spanning neutral co-ligand: Effect of anion inclusion and carboxylate pendant-arm length on topology and magnetism

Three divalent copper coordination polymers containing aromatic dicarboxylate ligands and the long-spanning tethering imine bis(4-pyridylmethyl)piperazine (bpmp) have been prepared and structurally characterized. The length of the dicarboxylate pendant arms, carboxylate binding mode, and the inclusion of anionic components play a synergistic role in structure direction in this system. {[Cu(ip)(bpmp)(H₂O)]·5H₂O}_n (ip = isophthalate, 1) displays neutral (4,4) rectangular coordination polymer grids that stack in an ABCD repeat pattern. Use of the longer pendant arm dicarboxylate 1,3-phenylenediacetate (phda) resulted in {[Cu₂(phda)₂(bpmp)]·H₂O}_n (2), a 3-D network coordination polymer with primitive cubic topology that features strongly antiferromagnetically coupled (J = −331(1) cm⁻¹) {Cu₂(CO₂)₄} paddlewheel units. In the presence of excess nitrate ions, {[Cu(phda)(Hbpmp)](NO₃)·3H₂O}_n (3) was isolated instead of 2; 3 manifests cationic 2-D coordination polymer layers built from weakly antiferromagnetically coupled (J = −2.43(1) cm⁻¹) {Cu₂O₂} dimers linked through phda and protonated bpmp ligands. The striking difference in magnetic properties is ascribed to the equatorial–equatorial versus axial–equatorial bridging of copper coordination spheres in 2 and 3, respectively.     

Novel thiocyanate complexes of cadmium(II) - Synthesis, spectroscopic characterization, X-ray studies and DFT calculations

Three novel thiocyanate cadmium(II) compounds [Cd(ind)₂(SCN)₂]_n (1), [Cd(dpa)Cl(SCN)]_n (2) and [Cd(terpy)(SCN)₂] (3) were synthesized and characterized by spectroscopic and crystallographic methods. Thiocyanate ions of 1 act as bridging ligands generating a one-dimensional chain constructed of Cd(SCN)₂Cd units and expanding along the crystallographic direction [1 0 0]. The Cd(II) ions of 2 are bridged by alternating di-μ-Cl and di-μ_1,3-NCS bridges to one-dimensional chain running along the crystallographic direction [0 1 0]. [Cd(terpy)(SCN)₂] (3) is a square pyramidal mononuclear compound.The fluorescence properties of the complexes 1 and 2 were examined in solid state, whereas fluorescence spectra of 3 were recorded in both solid state and solution. All they were compared with the fluorescence properties of the free ligands. Additionally, the electronic spectrum of 3 were investigated at the TDDFT level employing B3LYP functional in combination with LANL2DZ.     

Multinuclear NIR luminescent 1,4-BDC bridged Schiff-base complexes of Nd(III)

Solvent and reaction stoichiometry dictate the products isolated from reactions of the dinuclear precursor complex [ZnNdL(H₂O)(NO₃)₃] (H₂L = N,N′-bis(3-methoxy-salicylidene)ethylene-1,2-diamine) with the anionic multidentate linker 1,4-benzenedicarboxylate (1,4-BDC). With a 2:1 molar ratio of ZnNd:Na₂1,4-BDC in CH₃CN–EtOH the tetranuclear complex [Zn₂Nd₂L₂(1,4-BDC)(NO₃)₄(EtOH)₂] · 2MeCN (1) is produced while hexanuclear [Zn₄Nd₂L₄(1,4-BDC)₂] · (NO₃)₂ · 2Et₂O · 4H₂O (2) can be isolated from a DMF–EtOH mixture. A 4:1 mole ratio in DMF–EtOH gave the unusual polynuclear complex [Zn₄Nd₂L₄(1,4-BDC)₂] · [ZnNdL(NO₃)₃(OAc)]₂ (3). The NIR photophysical properties of the new compounds are reported.