Structural Characterization of Coordination Polymers of Nickel(II) and Zinc(II) with Polycarboxylate Ligands

Abstract  

The structural aspects of one-dimensional coordination polymer (1) of nickel(II) with 1,3,5-benzene tricarboxylate and a three-dimensional interpenetrating coordination polymer (2) of zinc(II) with 1,4-benzenedicarboxylate ligand are studied by single crystal X-ray diffraction analysis. Coordination polymer (1) forms a hydrogen bonded three dimensional network structures. The coordination polymer 1 having a composition [Ni₃(TMA)₂(H₂O)₁₂] _n where (TMA = trimesate anion), crystallizes in monoclinic crystal system with C2 space group and has a/?, 17.3387(4); b/?, 12.8748(4); c/?, 6.5302(2); β/°111.620(2); V/?³, 1355.20(7). The zinc coordination polymer 2 crystal system is orthorhombic, with space group Pbca. It has a/?, 14.5049(3); b/?, 17.1616(3); c/?, 18.1389(4); V/?³, 4515.27(16). The 1,4-benzenedicarboxylate three dimensional coordination polymer of zinc(II) comprises of novel hydroxo bridged tetranuclear zinc(II) secondary building units and has a composition [Zn₂(C₆H₄C₂O₄)_1.5{(CH₃)₂SO}₂(OH)] _n . Topological analysis of the three dimensional coordination polymer 2 shows that it has a two fold interpenetrating net topology.     

Syntheses,Structures and Luminescent Properties of Zinc(II) and Cadmium(II) Complexes With the Ditopic Ligand 1,3-Bis(imidazol-1-ylmethyl)benzene

Abstract  

Three new complexes, namely [Zn(mbix)(SO₄)]·CH₃OH (1), Cd(mbix)₂(NO₃)₂ (2) and [Cd(mbix)₂(H₂O)₂]·(NO₃)₂ (3), have been obtained by reactions of flexible bidentate ligand 1,3-bis(imidazol-1-ylmethyl)benzene (mbix) with corresponding zinc(II) and cadmium(II) salts. The structures of these complexes have been determined by the X-ray single crystal diffraction analysis. Complex 1 features a 2D wavy network with (4,4) topology. Complex 2 has a 2D grid network with left- and right-handed helical chains, while complex 3 exhibits twofold parallel interpenetration structure. The differences of three complexes demonstrate that the coordination geometry of metal ions and the ratio of reactants have a great impact on the structure of the supramolecular architectures. The luminescent properties of three complexes are also investigated.     

Syntheses,Crystal Structures and Fluorescence Properties of Zn(II) Complexes with Pyrazolone Derivatives

Abstract   N-(1,3-Diphenyl-4-benzal-5-pyrazolone)-salicylidene hydrazone(H₂L ¹ ) and its zinc complex Zn(HL ¹ )₂ · 2CH₃OH (1) have been synthesized and characterized by elemental analyses, IR spectra, thermal analyses and single-crystal X-ray diffraction studies. The X-ray diffraction analyses of the complex Zn(HL ¹ )₂ · 2CH₃OH (1) and the known compound Zn₄(L ² )₄ (2) (H₂L ²  = N-(1,3-diphenyl-4-phenylethylene-5-pyrazolone)-salicylidene hydrazone) show that different acyl groups in position 4 of pyrazolones may lead to the different coordination mode of the ligands and distinctive structures of the same central metal Zn(II) complexes, of which 1 is a mononuclear complex while 2 is a tetranuclear complex. Meanwhile, two Zn(II) complexes have different thermal stabilities and fluorescence properties. Graphical Abstract        

Hydrogen Bonded Supramolecular Network from a Mixed Valence Cobalt System: Synthesis and Crystal Structure of [Co(H2O)6][Co(pydc)2(en)]2·14H2O

Abstract  

The [Co(H₂O)₆][Co(pydc)₂(en)]₂·14H₂O (1) compound (H₂pydc = Pyridine-2,3-dicarboxylic acid and en = ethylenediamine) was synthesized and characterized by elemental analysis, magnetic and spectroscopic measurements (UV–Vis and IR spectra) and single crystal X-ray diffraction technique. There are two coordination spheres with different charges inside this aqueous compound of ionic character. The cationic part is composed of Co(II) encircled by six aqua ligand. Whereas the anionic part contains two anions complex unit each with −1 charge and have Co(III) ions in the centre. As a result different coordination spheres have cobalt ions with different states. The crystallographic analysis revealed that 1 consists of both discrete one-cationic and two-anionic entities, [Co(H₂O)₆]²⁺ and [Co(pydc)₂(en)]₂⁻ and fourteen crystal water molecules. Two water molecules within the water cluster act as hydrogen-bonding acceptors, whereas one water molecule acts as a hydrogen-bonding donor to form a discrete water trimer. These water molecules have stabilized the crystal structure by strong hydrogen bonding interactions.     

Synthesis, Crystal Structures and Properties of Two Copper (II) Complexes with Pyridazine Derivative Ligand

Abstract  Two new complexes, [Cu(L)₂(CH₃OH)] · (ClO₄)₂ (1) and [Cu(L)₂(H₂O)] · (NO₃)₂ (2), have been synthesized and their crystal structures have been determined by X-ray analysis, where L = 3-(3,5-bimethylpyrazole-yl)-6-chloro-pyridazine]. The complex 1 crystallizes in the monoclinic, space group C2/c, and the coordination configuration of copper (II) is better described as trigonal pyramidal geometry with four N atoms from L and one O_methanol^. The coordination configuration of 2 is quite similar to that of 1 except O_water instead of O_methanol^. The intermolecular hydrogen bonds link the repeat units and extend the molecules to multinuclear structures in both compounds. The spectral properties of the title compounds have been studied and discussed. Furthermore, the antibacterial activities of the title compounds have been detected, the results indicate that the ligands and two copper(II) complexes exhibit certain fungicidal activities again several bacteria. Index Abstract  Two new complexes, [Cu(L)2(CH3OH)]·(ClO4)2 (1) and [Cu(L)2(H2O)]·(NO3)2 (2), have been synthesized and their crystal structures have been determined by X-ray analysis, where L= 3-(3,5-bimethylpyrazole-yl)-6-chloro-pyridazine. The intermolecular hydrogen bonds extend the molecules to multinuclear structures in both compounds.      

Nickel(II) and Cobalt(II) Complexes with Symmetrical Four-Dentate Ligands: Crystal Structures,Characterization, and Initial DNA Binding Mechanism Research

Abstract  

Four new nickel(II) and cobalt(II) complexes of Schiff base ligands: [Ni(L)Cl₂]·2H₂O (I), [Ni(L)(H₂O)₂] (NO₃)₂ (II), [Ni(L)(H₂O)₂] (ClO₄)₂ (III), and [Co(L) (H₂O)₂] (NO₃)₂ (IV) (L = 1,3-[bis(pyridine-2-imino)]propane) have been synthesized. The four complexes have been fully characterized by elemental analysis, IR, absorption spectra, emission spectra, and single-crystal X-ray diffraction analysis. The binding of the four complexes to calf thymus DNA (CT DNA) has been investigated by absorption spectra and emission spectra. The results of the two methods indicate that the action mode of complex I with DNA is intercalative mainly, and the action mode of complexes II, III, IV with DNA cannot be concluded, it should be sustained by other experimental measurements.     

Self-Assembly of Two Isomorphous Thiocyanate Complexes of Co(II) and Ni(II) with 3-Hydroxypicolinamide

Abstract  

The synthesis, thermal and spectral characterization, and crystal structure of isomorphous thiocyanate cobalt(II) and nickel(II) complexes with 3-hydroxypicolinamide (3-OHpia), [M(C₆H₆N₂O₂)₂(NCS)₂]·2H₂O, are reported. The metal(II) ions are chelated by two cis-oriented 3-OHpia and two thiocyanate ligands in distorted octahedral geometry. The distortion within the coordination sphere is mainly imposed by formation of the chelate rings. The compounds crystallize in monoclinic space group P2/c with two symmetrically independent molecules and a = 14.4945(2) ?, b = 8.5906(1) ?, c = 16.3865(3) ?, β = 105.987(2)°, Z = 4 (1) and a = 14.4927(5) ?, b = 8.5912(3) ?, c = 16.2712(6) ?, β = 105.740(4)°, Z = 4 (2). Commonly observed supramolecular amide synthons are not robust enough to accommodate thiocyanate ions and H₂O molecules. But instead, neutral complexes are linked through hydrogen bonds leading to two different hydrogen bonding ribbon motifs involving amide moieties and H₂O molecules [C(8)R ₂²(12) along c axis] and amide moieties and thiocyanate ions [C(8)R ₂²(16) along b axis] for symmetrically related molecules labelled as 1 [Co1 (1) and Ni1 (2)] and 2 [Co2 (1) and Ni2 (2)], respectively.     

Self-Assembled Hydrogen-Bonding Chains of Copper(II) 2-Nitrobenzoate with Nicotinamide

Abstract  

The synthesis, spectral characterization and crystal structure of two new nitrobenzoatocopper(II) complexes, namely, [Cu₂(2-O₂Nbz)₄(nia)₂]·ACN (1) and [Cu₂(2-O₂Nbz)₄(ACN)₂] (2) (where 2-O₂Nbz = 2-nitrobenzoate, nia = nicotinamide and ACN = acetonitrile) are reported. The complexes 1 and 2 form dinuclear units of the paddle-wheel type around the crystallographic inversion centers. The copper ions are bridged by four 2-nitrobenzoate anions and the neutral N-donor ligands, viz. nicotinamide in 1 and acetonitrile in 2, are coordinated at apical positions. Selected geometric parameters of both complexes are compared with values for related tetra-2-nitrobenzoate complexes of copper(II) as well as the other dimeric copper(II) carboxylates with apical nicotinamide and acetonitrile ligands. The molecules of 1 are linked with N–H···O and C–H···O hydrogen bonds. The π–π stacking interactions in 1 are observed between benzene rings of 2-nitrobenzoate anions and pyridine rings of nicotinamide and also between acetonitrile molecules and benzene rings of 2-nitrobenzoate anions. The C–H···O hydrogen-bonds and CH/π interactions are observed in crystal structure of 2.     

A Unique Example of a Co-crystal of [Co(AMTTO)2(H2O)2](NO3)2 and [Co(AMTTO)2(CH3CN)2](NO3)2 (AMTTO = 4-amino-5-methyl-1,2,4-triazol-3(2H)-thione)

A co-crystal of cobalt(II) complexes, Co(AMTTO)₂(CH₃CN)₂]²⁺(NO₃)₂. [Co(AMTTO)₂(H₂O)₂]²⁺(NO₃)₂, compound (1) was isolated from the reaction of Co(NO₃)₂?6H₂O and 4-amino-3-mercapto-6-methyl-5-oxo-1,2,4-triazine (AMTTO) in acetonitrile as solvent. Isolated crystals were characterized by elemental analyses, IR spectroscopy as well as X-ray diffraction studies. Crystal data for 1 at 95 K revealed a monoclinic space group P2₁/n, a?=?11.7903(5), b?=?12.1279(5), c?=?14.1443(6) Å, β?=?99.244(4)°, Z?=?2, R₁?=?0.0339. Compound 1 consists of two co-crystallized Co(II) complexes [Co(AMTTO)₂(CH₃CN)₂]²⁺ and [Co(AMTTO)₂(H₂O)₂]²⁺ and four nitrate counter anions In both complexes, cobalt(II) ions are in an octahedral arrangement. Two S, N bidentate AMTTO ligands are coordinated to both Co(II) ions. The coordination sphere of Co1 is completed by two acetonitrile molecules, and these positions are occupied by water molecules for Co2.

Graphic Abstract

A co-crystal of cobalt(II) compound was isolated from the reaction of Co(NO₃)₂?6H₂O and 4-amino-3-mercapto-6-methyl-5-oxo-1,2,4-triazine in acetonitrile as solvent.

     

Pyridine-2,6-Dicarboxylic Acid (Dipic): Crystal Structure from Co-Crystal to a Mixed Ligand Nickel(II) Complex

Abstract  

Pyridine-2,6-dicarboxylic acid (dipic) was used for the synthesis of a co-crystal with 1,10-phenanthroline-5,6-dione (phen-dione) and a nickel(II) complex. The co-crystal dipic·phen-dione·4H₂O (1) has been synthesized and studied by X-ray crystallography. The structure is stabilized with hydrogen bonds between dipic, H₂O and phen-dione. It is surprising that there is no direct hydrogen bonding between phen-dione and dipic and yet the molecules co-crystallize in aqueous solution. A new complex of nickel(II), [Ni(phen)(dipic)(H₂O)]·4H₂O (2), (where phen = 1,10-phenanthroline) has been synthesized and characterized by elemental and thermogravimetric analyses, FT-IR, UV–Vis and ¹H-NMR spectroscopy. The structure of (2) has been studied by X-ray crystallography. The coordination around Ni(II) is a distorted octahedron. The crystal packing shows that the dimensionality of (2) is enlarged to 3D, through hydrogen bonds and π–π interactions. Cyclic voltammetry of (2) shows that the Ni(II/I) couple is irreversible.     

Neutral Praseodymium(III) Complexes with Tetraselenidoantimonate Ligand: Coligand Influence of Mixed Polyamines on the Coordination Mode of [SbSe4]3? Anion

Abstract  

Mix-coordinated praseodymium(III) complexes concerning the [SbSe₄]³⁻ inorganic ligand, [Pr(en)₂(dien)(η ²-SbSe₄)] (1) and [Pr(en)(trien)(μ-η ¹,η ²-SbSe₄)] _n (2) (en = ethylenediamine, dien = diethylenetriamine, trien = triethylenetetramine), were prepared by solvothermal reactions of Pr₂O₃, Sb and Se in en + dien and en + trien mixed solvents, respectively. They crystallize in the monoclinic space group P2₁/n but with different molecular structures. Crystallographic data for 1: a = 8.610(2), b = 27.722(7), c = 9.294(2) ?, β = 108.987(3)°, V = 2097.7(9) ?³, Z = 4. For 2: a = 14.2987(17), b = 9.0176(9), c = 15.4357(18) ?, β = 100.708(3)°, V = 1955.6(4) ?³, Z = 4. The [SbSe₄]³⁻ anion coordinates to the Pr³⁺ ion in [Pr(en)₂(dien)]³⁺ as a η ²-SbSe₄ chelating ligand, yielding complex 1. It acts as a μ-η ¹,η ²-SbSe₄ bridging ligand to connect the [Pr(en)(trien)]³⁺ ions into the polymer 2. The coordination difference between 1 and 2 is attributed to the coligands of mixed polyamines.     

Synthesis and Crystal Structure of Phenolato-Bridged Dinuclear Copper(II) Complex with (2-Hydroxybenzyl)(2-pyridylmethyl)amine

Abstract  

The tridentate Schiff base phenol-containing ligand (2-hydroxybenzyl)(2-pyridylmethyl)amine (Hbpa) reacts with copper(II) perchlorate to give the phenolato-bridged dinuclear complex [Cu(bpa)(H₂O)]₂·2ClO₄ (1). Each copper(II) ion exhibits a distorted square-pyramidal environment, being coordinated by two nitrogen atoms and two phenolato oxygen atoms of the two deprotonated bpa ligands, and one oxygen atom of the water molecule. It crystallizes in the triclinic system P-1 with a = 7.8790(6), b = 8.9345(7), c = 12.0207(9) ?, α = 69.158(1), β = 85.307(1), γ = 76.629(1)°, V = 769.39(10) ?³, Z = 1. Cyclic voltammetry of 1 gives two oxidation and two reduced processes.     

Synthesis and Crystal Structures of Copper(II) Complexes Derived from 5-Methoxy-2-[(2-morpholin-4-ylethylimino)methyl]phenolate and (2-Morpholin-4-ylethyl)-(1-pyridin-2-ylethylidene)amine

Abstract  

A pair of copper(II) complexes, [CuL¹(ONO₂)(OH₂)] 1 and [CuBrL²N₃] 2, where L¹ is 5-methoxy-2-[(2-morpholin-4-ylethylimino)methyl]phenolate, and L² is (2-morpholin-4-ylethyl)-(1-pyridin-2-ylethylidene)amine, have been synthesized and characterized by elemental analysis, IR spectra and single crystal X-ray diffraction. Complex 1 crystallizes in the monoclinic space group P2₁/c, with a = 10.496(2), b = 19.113(3), c = 8.586(2) ?, β = 105.186(10)°. Complex 2 crystallizes in the monoclinic space group C2/c, with a = 16.606(3), b = 7.357(2), c = 26.043(5) ?, β = 94.996(2)°. The Cu atom in each complex is five-coordinate in a square pyramidal geometry.     

Synthesis and Crystal Structure of a Complex of Palladium(II) with 2-Hydroxyimino-3-(2-hydrazonopyridyl)-butane

Abstract  

Schiff-base condensation of an equimolar proportion of diacetyl-monoxime and 2-hydrazino pyridine in methanol gives rise to 2-hydroxyimino-3-(2-hydrazonopyridyl)-butane (HL). The ligand has been characterised by FT-IR, ¹H NMR and UV–Vis spectra. Reaction of 1:1 stoichiometric proportion of HL with Na₂[PdCl₄] in methanol affords a mononuclear palladium(II) compound, [PdLCl]·H₂O (1). The compound is characterised by C, H and N analyses, FT-IR, conductivity measurement, UV–Vis spectra, thermal analysis and magnetic susceptibility measurement. The X-ray crystal structure of the title compound (1) has been determined. The compound crystalises in the triclinic space group P[`1] P\overline{1} with a = 7.3033(3), b = 9.4139(4), c = 9.4445(5) ?, α = 79.789(3), β = 68.285(2), γ = 77.978(3)o, V = 586.42(5) ?³ and Z = 2. Pd(II) is in ‘N₃Cl’ coordination chromophore. The geometry around Pd(II) is square-planar. The compound is essentially diamagnetic.     

Ligand Substitution Chemistry of the Diphosphine Ligand endo,endo-2,3-Bis(diphenylphosphinomethyl)-5-norbornene (dpmn): Syntheses and X-ray Diffraction Structures of PtCl2(dmn) and PtMe2(dpmn)

Abstract  The reaction of phosphine ligand endo,endo-2,3-bis(diphenylphosphinomethyl)-5-norbornene (dpmn) with PtCl₂(cod) and PtMe₂(cod) yields PtCl₂(dpmn) (2) and PtMe₂(dpmn) (4), respectively. Treatment of 2 with excess MeLi or MeMgCl also furnishes 4 in good yield. Both new platinum compounds have been isolated and characterized by NMR spectroscopy (¹H and ³¹P), elemental analyses, and X-ray crystallography. 2 Crystallizes, as the CH₂Cl₂ solvate, in the orthorhombic space group Pnma, a = 18.062(3) ?, b = 16.602(3) ?, c = 11.088(2) ?, V = 3,324.7(9) ?³, Z = 4, D _cacl = 1.681 mg/m³; R = 0.0432, R _w = 0.0759 for 3,755 observed reflections with I > 2σ(I). 4 Crystallizes, as the CH₂Cl₂ solvate, in the orthorhombic space group Pnma, a = 17.969(3) ?, b = 16.689(3) ?, c = 11.237(2) ?, V = 3,370(1) ?³, Z = 4, D _cacl = 1.610 mg/m³; R = 0.0268, R _w = 0.0665 for 4,098 observed reflections with I > 2σ(I). The solid-state structures of 2 and 4 confirm the coordination of the platinum(II) center by the seven-membered chelating dpmn ligand; 2 and 4 represent the first structurally characterized examples of organometallic compounds based on the endo,endo-2,3-bis(diphenylphosphinomethyl)-5-norbornene ligand. Graphical Abstract  The new platinum(II) compounds PtCl₂(dpmn) (2) and PtMe₂(dpmn) (4) have been synthesized, and their structures established by NMR spectroscopy (¹H and ³¹P) and X-ray crystallography. Compounds 2 and 4 are the first structurally characterized examples of organometallic compounds containing the endo,endo-2,3-bis(diphenylphosphinomethyl)-5-norbornene (dpmn) ligand.

Ultrafast Optical Response in Quasi-One Dimensional Halogen-Bridged Mixed-Valence Complexes [Pt(en)2][PtBr2(en)2](ClO4)4 and [Pd(en)2][PdCl2(en)2](ClO4)4

Abstract

Ultrafast optical response in two quasi-one-dimensional halogen-bridged mixed-valence complexs [Pt(en)₂][PtBr₂(en)₂](ClO₄)₄ (en=ethylenediamine) (abbreviated as PtBr) and [Pt(en)₂][PtBr₂(en)₂](ClO₄)₄ (as PdCl) has been investigated by femtosecond absorption spectroscopy at room temperature by pump-probe spectroscopy. The photo-induced absorption around 1.3 eV and the bleaching from 1.5 eV to 2.7 eV were observed in PtBr. Both consist of a fast-decay component due to STEs and a slow-decay component due probably to polaron pairs. The former decays exponentially with the time constant of 1.4 ± 0.2 ps. The latter decays as erf(t ^β) with β = -0.22 ± 0.02, indicating the geminate recombination of an electron polaron and a hole polaron after moving freely along the chain. The deviation of β from the ideal random-walk model (β = -0.5) is explained by introducing the effect of potential barrier between the polarons hindering the recombination. A pump-probe absorption spectrum of PdCl is obtained from the reflection spectrum by the Kramers-Kronig relations. The time dependence of the transient photoinduced absorption around 1.7 eV and the bleaching from 1.9 eV to 2.5 eV were calculated to be described with three components. They correspond to free excitons with lifetime of about 800 fs, self-trapped excitons with lifetime of about 3 ps, and polaron pairs which hardly relax within 100 ps.     

Crystal Structure of [Zn(2-Bromobenzoato)<Subscript>2</Subscript>]<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> and [Zn(2-Bromobenzoato)<Subscript>2</Subscript>(<Emphasis Type="Italic">N</Emphasis>-Methylnicotinamide)]<Subscript>2</Subscript>

Abstract  

The syntheses and structural characterizations of two novel 2-bromobenzoatozinc(II) complexes—[Zn(2-BrC₆H₄COO)₂] _n (I) and [Zn(2-BrC₆H₄COO)₂(mnad)]₂ (II), where mnad is N-methylnicotinamide are reported. Compound (I) crystallized with a monoclinic lattice (space group P2₁/c) and is polymeric in solid state. Its cell parameters are: a = 7.37220(10) Å, b = 19.9639(3) Å, c = 30.2756(5) Å, β = 94.7510(7)°, V = 4440.59(12) ų, Z = 4. The coordination environments of all zinc atoms are distorted tetrahedra built from four carboxylate oxygen atoms coming from four 2-bromobenzoato ligands. Compound (II) crystallized with a monoclinic lattice (space group P2₁/c) with a = 11.7488(2) Å, b = 20.3683(3) Å, c = 9.30130(10) Å, β = 100.3941(11)°, V = 2189.30(5) ų, Z = 2. This dimeric molecule features a paddle-wheel [Zn₂O₈] cage in solid state; the coordination environment of the central atom is square pyramidal consisting of four carboxylate oxygen atoms and the pyridine N atom of the mnad ligand.     

New sulfur derivatives of 2,3-dichloropyrrolo[1,2-a] benzimidazol-1-one. Demonstration of regioselective thiolate addition and X-ray diffraction structures of 2-chloro-3-methylthiopyrrolo[1,2-a]benzimidazol-1-one and 2,3-di(benzylthio)pyrrolo[1,2-a]benzimidazol-1-one

The reaction of thiols with the heterocyclic compound 2,3-dichloropyrrolo[1,2-a] benzimidazol-1-one (1) has been investigated as a route to new redox-active, bidentate sulfur ligands. Treatment of 1 with either methylthiol or benzylthiol in the presence of pyridine affords monosulfide compounds 2-chloro-3-methylthiopyrrolo[1,2-a] benzimidazol-1-one (2) and 2-chloro-3-benzylthiopyrrolo[1,2-a]benzimidazol-1-one (3) and the disulfide derivatives 2,3-di(methylthio)pyrrolo[1,2-a]benzimidazol-1-one (4) and 2,3-di(benzylthio)pyrrolo[1,2-a]benzimidazol-1-one (5). The substitution of the first chlorine group in 2,3-dichloropyrrolo[1,2-a]benzimidazol-1-one (1) occurs regioselectively at C-3 to produce 2-chloro-3-methylthiopyrrolo[1,2-a]benzimidazol-1-one (2) and 2-chloro-3-benzylthiopyrrolo[1,2-a]benzimidazol-1-one (3), followed by replacement of the remaining chlorine group to furnish the disulfide compounds 4 and 5. The new thiols have been isolated by column chromatography and characterized in solution by spectroscopic methods. The molecular structures of 2-chloro-3-methylthiopyrrolo[1,2-a]benzimidazol-1-one and 2,3-di(benzylthio)pyrrolo[1,2-a]benzimidazol-1-one have been determined by X-ray crystallography. Compound 2 crystallizes as two independent molecules in the monoclinic space group P2₁/c, a = 13.221(2) Å, b = 18.478(2) Å, c = 8.948(1) Å, = 100.088(3)°, V = 2152.3(5) ų, Z = 8, and d_calc = 1.547 Mg/m³; R = 0.0354, R_w = 0.0739 for 2820 reflections with I > 2(I). Compound 5 crystallizes in the triclinic space group P-1, a = 5.180(1) Å, b = 11.494(2) Å, c = 17.243(3) Å, = 86.024(3)°, = 88.606(4)°, = 81.235(3)°, V = 1012.1(4) ų, Z = 2, and d_calc = 1.360 Mg/m³; R = 0.0354, R_w = 0.0692 for 2655 reflections with I > 2(I). The redox properties of the disulfide compounds 4 and 5 have been explored by cyclic voltammetry, where a one-electron reduction at ca. –1.10 V has been observed for each compound. The site of electron accession in has been established by carrying out molecular orbital calculations at the extended Hüuckel level on the model compound 2,3-di(thio)pyrrolo[1,2-a]benzimidazol-1-one.     

Synthesis and Crystal Structures of Anionic Gallium(II) and Gallium(III) Heterocyclic Compounds Derived from a Gallium(I) N-Heterocyclic Carbene Analogue

Abstract  

The addition of the N–H bond of the formamidine, ArN(H)C=NAr (Ar = C₆H₃Pr₂ⁱ-2,6), to the gallium(I) center of [K(tmeda)][:Ga(Ar-DAB)] (Ar-DAB={(Ar)NC(H)}₂) yields K[(Ar-DAB)Ga^III(H){N(Ar)C=NAr}] 1. The crystal structure of this and two other related anionic compounds, [K(18-crown-6)][(Ar-DAB)Ga^III{N(H)N=Fl}{(H)Fl}] (Fl = fluorendiyl) 2 and [K(OEt₂)₃][(Ar-DAB)Ga^II(CH₂Ph)Ga^II(Ar-DAB)] 3, have been determined. The cell parameters of the compounds are 1: P2₁/c, a = 20.2350(9), b = 14.1760(7), c = 19.6441(10), β = 111.307(1); 2: P2₁/c, a = 13.115(3), b = 21.799(4), c = 22.646(5), β = 90.20(3); 3: P2₁/n, a = 16.783(3), b = 21.635(4), c = 19.814(4), β = 92.34(3). The crystal structures of all complexes exhibit distorted tetrahedral gallium centers, and interactions between anion aryl substituents and the potassium cations.     

Synthesis,Properties, and Crystal Structures of Copper(II) Di-(2-picolyl)amine Complexes Containing Inorganic Salts

Abstract These complexes have been characterized by X-ray crystallography, spectroscopic, and cyclic voltammetry. In 1, the copper(II) ion has a distorted square-pyramidal geometry with three nitrogen atoms of the dpa ligand and two oxygen atoms of the nitrate anions. The crystal structure of 2 shows that the copper(II) ions are bridged by tp anion to form a dinuclear complex, in which each copper(II) ion exhibits a distorted square-pyramid with three nitrogen atoms of the dpa ligand, water molecule, and the oxygen atom of the bridging tp ligand. Cyclic voltammetric data indicate that 1 undergoes irreversible one-electron oxidation to the Cu^III and reversible one-electron reduction to the Cu^I, while 2 gives one reversible oxidation and two reversible and irreversible reduced processes. The electronic spectra and redox potentials of the complexes are influenced significantly by the anionic ligands. Graphical Abstract The reaction of [Cu(dpa)Cl₂] with K(NO₃)₂ and Na₂tp yields mononuclear and dinuclear copper(II) complexes [Cu(dpa)(NO₃)₂] (1) and [Cu₂(dpa)₂(H₂O)₂(μ-tp)](tp)·6H₂O (2) (dpa = di-(2-picolyl)amine, tp = terephthalate).