Synthesis, structural characterization and third-order non-linear optical property of new three-dimensional metal-organic polymer [Fe2(μ10-btc)0.5(μ2-ox)0.5(μ2-O)1.5]n

One new metal-organic polymer formulated as [Fe₂(μ₁₀-btc)_0.5(μ₂-ox)_0.5(μ₂-O)_1.5]_n 1 (btc = 1,2,4,5-benzenetetracarboxylate, pyramellitate; ox = oxalate) has been synthesized by low-temperature solid-state reaction and characterized by single-crystal X-ray diffraction, elemental analyses, TGA, IR spectra and UV–visible spectra. Complex 1 presents the first 3D coordination network structure constructed by bridging btc, ox and O mixed ligands. In 1, carboxyl groups of btc are all deprotonated and they have a new type of μ₁₀-btc coordination mode. The third-order non-linear optical (NLO) properties of the title compound 1 were also investigated and they exhibit the reverse saturable absorption and self-defocusing performance with modulus of the hyperpolarizability (γ) 5.98 × 10⁻³⁰ esu for 1 in a 7.45 × 10⁻⁴ mol dm⁻³ DMF solution.     

Hetero-bimetallic 2D coordination network constructed by azacrown ether carboxylic acid with lanthanide(III) and sodium ions

Two lanthanide-based coordination polymers [Na₃La(L)Cl·(H₂O)₆]·NO₃ (La-L) and [Na₃Eu(L)Cl·(H₂O)₆]·NO₃ (Eu-L) were newly synthesized by reaction of an azacrown ether carboxylic acid ligand H₄L (4,7,13,16-tetracarboxymethyl-1,10-dioxa-4,7,13,16-tetraazacyclooctadecane) with La(III)/Eu(III). Complexes La-L and Eu-L exhibited two-dimensional (2D) coordination architectures built up by Ln–L coordinating subunits and one-dimensional (1D) Na–O bridging chains. Four versatile coordination modes of carboxyl groups and Na–O coordination bi-chains linked by novel μ-O bridges (μ2-O and μ3-O) were demonstrated in the structure. Photoluminescence spectra of Eu-L were investigated to reveal characteristic emissions of Eu(III). This is the first example of hetero-bimetallic complex of the tetraazacrown ether ligand with lanthanide and sodium ions.     

Diplatinum(III) [Cl2(μ2-amidinate)4] compound derived from air oxidation of mononuclear cis-[Pt(NH3)2(amidine-κ)2] complex

The dinuclear platinum(III) complex [Pt₂Cl₂{μ₂-N(H)C(Et)N(H)}₄] (2) has been prepared by heating cis-[Pt(NH₃)₂{NHC(NH₂)Et}₂](Cl)₂ (cis-1) under aeration conditions in an EtOH/H₂O mixture at 70 °C for 2 d and it was characterized by elemental analyses (C, H, N), ESI⁺-MS, IR, ¹H and ¹³C NMR spectroscopies and also by X-ray diffraction. Complex 2 represents the second Pt^III dimer stabilized by the amidinate ligand ever known and it has a lantern-type structure with four amidinate ligands bridging two Pt^III centers with Pt–Pt distance of 2.4809(2) Å.     

The system iron(II)/mpzbpy mediates the H2O2 oxidation of cyclohexane and cyclooctene and the aerobic oxidative cleavage of ascorbic acid to oxalate

The iron complex generated in situ from Fe(CF₃SO₃)₂ and the new tridentate N ligand mpzbpy (mpzbpy stands for 6-(3,5-dimethylpyrazol-1-ylmethyl)-6′-methyl-2,2′-bipyridine) mediates the room temperature oxidation of cyclohexane to cyclohexanol and cyclohexanone, and the epoxidation of cyclooctene to cyclooctene oxide. X-ray diffraction studies of single crystals obtained by reaction of iron(II) triflate with mpzbpy in methanol in the presence of ascorbic acid reveals the formation of a dinuclear complex, namely [Fe₂(mpzbpy)₂(C₂O₄)(CF₃SO₃)₂] (1), where two iron(II) ions are bridged by an oxalato dianion originating from the oxidative cleavage of ascorbic acid. Magnetic susceptibility measurements of 1 show that the two metallic centres are weakly antiferromagnetically coupled, with a J value of −1.74(1) cm⁻¹.     

Reaction between the diaqua form of cisplatin and 2-methylsulfanylphenylphosphonic acid yields a dinuclear phosphonato-bridged complex via NH3 elimination

Reaction between cis-[Pt(NH₃)₂(H₂O)₂]²⁺ and (2-methylsulfanyl)phenyl phosphonic acid (H₂mspp) did not yield the expected cis-diammine [(2-methylsulfanylphenyl)phosphonato]platinum(II) but the dimeric compound [{Pt(mspp)(NH₃)}₂]·6H₂O in which the dianionic mspp²⁻ ligand acts both as chelator and bridging ligand. Thus, the high trans-effect of the sulfanyl group apparently leads to elimination of one NH₃ ligand. An X-ray crystal structure analysis of the dimeric complex is reported.     

The dipeptide H-Aib-l-Ala-OH ligand in copper(II) chemistry: Variation of product identity as a function of pH

A systematic investigation of the influence of “pH” on the product identity from the Cu^II/H-Aib-l-Ala-OH (LH) reaction system is described, where H-Aib-l-Ala-OH is α-aminoisobutyryl-l-alanine. The pH variation has led to the synthesis of two discrete complexes, the structures of which have been determined by single-crystal X-ray crystallography. The “low pH” complex {[CuClL](H₂O)_2.5}_n (1) is a 3D coordination polymer, in which the dipeptide monoanion L⁻ behaves as a η¹:η¹:η¹:μ₂ ligand binding one Cu^II atom through its amino nitrogen and neutral peptide oxygen, and an adjacent Cu^II atom through one of its carboxylate oxygen. The “higher pH” complex {[Cu(H₋₁L)(EtOH)](EtOH)}_n (2) is a chain (1D) compound, in which the dipeptide dianion H₋₁L²⁻ uses its amino nitrogen, deprotonated peptide nitrogen and both carboxylate oxygens to bridge two metal centres.     

Solvothermal synthesis of a novel mixed valence Cu(I)/Cu(II) complex containing sulphate, malate and 4,4-bipyridine, [CuCu2(mal)(SO4)(bpy)2 · H2O]n. Unique binding mode of the malate anion

The reaction of CuSO₄ · 5H₂O with 4,4^′-bipyridine and malic acid at 140 °C under solvothermal conditions afforded a mixed valence three-dimensional coordination polymer [Cu^ICu^II₂(mal)(SO₄)(bpy)₂ · H₂O]_n, (1). The building unit consists of a Cu²⁺-dimer in which copper centers are bridged by malate and sulphate anions. SO₄²⁻ anion further connects dimeric unit with the Cu¹⁺ center. Building units are linked by 4,4^′-bipyridine ligands to form double chains, that are interconnected into 3D network through additional sulphate bridge.     

Hemiprotonated dafone,a new cationic species. The novel di-dafonium iron(III) complex: [(dafone)2H]+[FeCl4]−

The reaction of dafone (4,5-diazafluoren-9-one, 1) and iron(III) chloride in concentrated hydrochloric acid medium yields an unusual complex containing hemiprotonated dafone, [(dafone)₂H]⁺[FeCl₄]⁻. The crystal structure reveals that two coordinating ligands share a single proton to form the new cation [(dafone)₂H]⁺ while the accompanying tetrachloroferrate(III) anion stabilizes the ion pair. The [FeCl₄]⁻ anion is close to tetrahedral in geometry with four chloro ligands in the first coordination sphere which is only slightly affected by the interactions with the di-dafonium unit.     

Novel Hg and Mn supramolecular complexes with a versatile building block 5-(4-pyridyl)-1,3,4-oxadiazole-2-thiolate involving in situ ligand formation

Reaction of potassium N′-(pyridine-4-carbonyl)-hydrazinecarbodithioate ([K⁺(H₂L)⁻]) with Hg^II or Mn^II inorganic salt in the presence of 1,10-phenanthroline (phen) or 4,4′-bipyridine (bipy), yields complexes [Hg(pyt)₂(phen)] (1) and {[Mn(pyt)₂(H₂O)₂]·(bipy)·(H₂O)₂}_n (2), in which the pyt ligand (Hpyt = 5-(4-pyridyl)-1,3,4-oxadiazole-2-thiol) is obtained by in situ ligand formation from the acyclic precursor [K⁺(H₂L)⁻]. Single crystal X-ray diffraction suggests that the pyt anionic ligands in 1 and 2 behave as thiolate and thione isomers, respectively, and display S- and μ-N_pyridyl, N_oxadiazole-binding fashions. Complex 1 shows a 1-D fishbone-like supramolecular array via strong aromatic stacking interactions between the discrete mononuclear coordination motifs, whereas 2 has a 2-D layered host coordination framework with the inclusion of bipy and water guests in the cavities.     

Catalytic properties of Ru-η-C6H6-diphosphine complexes for hydrogenation of benzene in aqueous-organic biphasic system

The influences of pH on the catalytic properties of Ru-η⁶-C₆H₆-diphosphine complex [RuCl(η⁶-C₆H₆)(BISBI)]Cl (1) (BISBI = 2,2′-bis(diphenylphosphinomethyl)-1,1′-biphenyl), [RuCl(η⁶-C₆H₆)(BDPX)]Cl (2) (BDPX = 1,2-bis(diphenylphosphinomethyl)benzene), Ru₂Cl₄(η⁶-C₆H₆)₂(μ₂-BDNA) (3) (BDNA = 1,8-bis(diphenylphosphinomethyl)naphthalene), [RuCl(η⁶-C₆H₆)(BISBI)]BF₄ (4), [RuCl(η⁶-C₆H₆)(BDPX)]BF₄ (5), and [(η⁶-C₆H₆)₂Ru₂Cl₂(μ₂-Cl)(μ₂-BDNA)]BF₄ (6) for the hydrogenation of benzene were investigated in aqueous-organic biphasic system. The hydrogenation of benzene catalyzed by all complexes yielded only cyclohexane. The catalytic results revealed that the stabilities of these complexes were not only closely relative with their compositions or molecular structures but also the pH value of aqueous solution. Complexes 1 and 2 were homogeneous catalysts at pH <5, but complexes 3, 4, 5 and 6 were partly decomposed in the same reaction conditions and played simultaneously the roles of homogeneous and heterogeneous catalysts. When the pH was up to 12, all of six complexes were gradually decomposed to Ru(0) particles. The addition of extra phosphine ligand was favorable to prevent these complexes from decomposing in the catalytic process. The experiment of mercury poisoning and the curve of conversion vs time strongly supported above conclusions.     

Ferromagnetic coupling in a novel dicyanamide-bridged dinuclear gadolinium(III) complex [Gd2(dca)4(OH)2 (NITpPy)4] (NITpPy = 4-pyridyl-nitronyl nitroxide radical)

The novel six-coordinated gadolinium(III) complex of formula [Gd₂(dca)₄(OH)₂(NITpPy)₄] (1) (dca = dicyanamide, NITpPy = 4-pyridyl-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-oxy-3-oxide) has been prepared and characterized by X-ray crystallography. Compound 1 is a dimer structure made up of double μ_1,5-dca-bridged gadolinium(III) ions and one terminal dca ligand; variable-temperature magnetic susceptibility measurements reveal the occurrence of a significant ferromagnetic interaction directly spin polarization through the NITpPy–Gd(III)–NITpPy pathway with J = 11.56 cm⁻¹.     

Synthesis and characterization of macrocyclic nickel(II) complexes with α-methylbenzyl groups as chiral pendants

Novel nickel(II) hexaaza macrocyclic complexes, [Ni(L^R,R)](ClO₄)₂ (1) and [Ni(L^S,S)](ClO₄)₂ (2), containing chiral pendant groups have been synthesized by an efficient one-pot template condensation and characterized (L^R,R/S,S = 1,8-di((R/S)-α-methylbenzyl)-1,3,6,8,10,13-hexaazacyclotetradecane). The crystal structures of 1 and 2 were determined by single-crystal X-ray analysis. Each complex has a square-planar coordination environment for the nickel(II) ion, and is either an R or an S enantiomorph depending on the pendant groups. The circular dichroism spectrum of 1 showed a negative, positive and negative peak at 345, 440, and 492 nm, respectively, and that of 2 exhibited an enantiomeric pattern.     

Pseudo-isomeric zinc/copper coordination polymers based on 3-(2-pyridyl)pyrazole-5-carboxylic acid

Reaction of 3-(2-pyridyl)pyrazole-5-carboxylic acid (H₂L) with Zn(II) or Cu(II) perchlorate yielded [ZnL]_n (1) and [CuL]_n (2) with similar composition. The ligand L^2 − adopts the same μ₃κ⁵ coordination mode. The Zn(II) and Cu(II) atom takes square pyramid coordination polyhedron with some discrepancy. Bigger difference in the dimeric secondary building blocks leads to distinct two-dimensional metal–organic frameworks. The Zn(II) complex fluoresces stronger than the free ligand. The Cu(II) polymer displays strong antiferromagnetic intra-dimer exchange and ferromagnetic inter-dimer exchange.     

Synthesis, crystal structures and photoluminescence properties of Sm-based enantiomeric pair

Novel Sm-based enantiomeric pair, generally formulated Sm(DBM)₃L (L_R,R in 1, L_S,S in 2, DBM = dibenzoylmethanate) have been successfully prepared via the reaction of Sm(DBM)₃·2H₂O with chiral ligands L_R,R (−)-4,5-pinene bipyridine and L_S,S (+)-4,5-pinene bipyridine (Scheme 1), respectively. The crystal structure analysis of 1 and 2 reveal that they crystallize in chiral space group P2₁ of monoclinic system. The central Sm(III) ion is octacoordinate with six β-diketonate oxygen atoms and two chiral pinene bipyridine nitrogen atoms, forming a coordination polyhedron best described as the distorted square antiprism (SA). The CD spectra (Fig. S1) further confirm that 1 and 2 are enantiomers. The photoluminescence investigations of 1 and 2 demonstrate that they display deep-red luminescence characteristic of the Sm³⁺_.     

Assembly of a novel luminescent coordination polymer from europium nitrate and a new semirigid bridging podand

One-dimensional zig-zag coordination polymer has been rationally assembled by the reaction of europium nitrate and a new amide type semirigid bridging podand 1,4-bis{[(2′-m-picolylaminoformyl)phenoxyl]methyl}naphthalene (L). The coordination chains are further linked by the intermolecular hydrogen bonds to form two-dimensional supramolecular layer structure. At the same time, the luminescent properties of the Eu(III) complex were also investigated. Under the excitation, the complex exhibited characteristic emissions of europium ion.     

Solvothermal in situ formation of a hexanuclear copper(I) complex with 2-thiolate-N,N′-dimethylnicotinamide

Solvothermal reaction of 2-mercaptonicotinic acid (HL¹) with copper(II) nitrate in DMF/methanol medium leads to the production of a novel hexanuclear complex [Cu(L²)]₆ · (H₂O)₂ (1), in which in situ formation of an anionic ligand 2-thiolate-N,N′-dimethylnicotinamide (L²) and reduction of copper(II) to copper(I) are observed. X-ray single-crystal structure of 1 reveals that each copper(I) center adopts a trigonal geometry provided by two thiolate and one pyridyl groups from three separated L² ligands. As a result, six copper(I) ions are interconnected by six μ₃–L² bridges to afford a hexanuclear cluster, in which the octahedral Cu₆ core is stabilized by significant cuprophilic interactions.     

First dicadmium(II) complex of tripodal amide ligand with one edge-sharing monocapped octahedral geometry

A new dicadmium(II) complex [Cd₂(L)₂(H₂O)₂](NO₃)₄ · 8H₂O (1) with the tripodal amide ligand L (tris[3-aza-2-oxo-4-(2-pyridyl)butyl]amine) was synthesized and structurally characterized. Complex 1 is revealed as a dinuclear 2:2 (Cd:L) complex, in which each cadmium(II) ion is hepta-coordinated with the coordination surrounding of distorted monocapped octahedral geometry. Two cadmium(II) ions are dibridged by two carbonyl μ-O atoms forming a Cd₂(μ-O)₂ parallelogram-type moiety. Interestingly, the dinuclear coordination sphere can be seen as resulting from the fusion of two distorted monocapped octahedral [Cd(L)(H₂O)]²⁺ units through sharing one edge originated from the two carbonyl μ-O atoms as a first example. Comparative NMR, IR and FAB-mass data of 1 are also discussed.     

N-Picolyl-N′-benzoylthiourea, H2picbtu – A new ligand with a remarkable coordination mode. Synthesis and structures of H2picbtu and its tetrameric oxorhenium(V) complex

(NBu₄)[ReOCl₄] reacts with N-picolyl-N′-benzoylthiourea (H₂picbtu) in acetone under formation of the deep-green oxorhenium(V) complex (NBu₄)₂[{Re₂O₂Cl₅(Hpicbtu)}₂O], which was studied by X-ray diffraction. Two dimeric units with each one bridging, singly deprotonated thiourea ligand are connected by an oxo ligand. Inside the subunits, Hpicbtu⁻ coordinates as S,O chelate with a six-membered chelate ring to one rhenium atom, while a five-membered chelate ring is established with the second Re atom and the nitrogen atoms of the picolylamine building block. The compound represents one of the very rare examples of anionic μ-oxorhenium(V) complexes.     

Structure and magnetic properties of a novel branch-like one-dimensional cyano-bridged assembly [Cu(L)]3[Fe(CN)6]2·8H2O (L = 6,13-dimethyl-6-nitro-1,4,8,11-tetraazabicyclo[11.1.1]pentadecane)

The one-dimensional coordination polymer like fern branch, [Cu^II(L)]₃[Fe^III(CN)₆]₂·8H₂O (1), which is linked by azamacrocyclic copper(II) complex and iron(III) hexacyanide, has been synthesized and characterized by single crystal X-ray crystallography and magnetic susceptibility measurement (L = 6,13-dimethyl-6-nitro-1,4,8,11-tetraazabicyclo[11.1.1]pentadecane). Compound 1 shows a weak ferromagnetic coupling between the copper(II) and low spin iron(III) ions in the one-dimensional chain structure.     

Two novel isomeric complexes supported by vanadates {V4O12}: [{Cu(dpa)2}2V4O12] (dpa = 2,2′-dipyridylamine)

Two Cu(II) complexes supported by tetravanadates, [{Cu(dpa)₂}₂V₄O₁₂] (1 and 2), have been synthesized under hydrothermal reactions. Structural analysis indicates that complexes 1 and 2 are isomeric and consist of a cyclic [V₄O₁₂]^4- anion bridged to two [Cu(dpa)₂]²⁺ moieties. Close inspection of complexes 1 and 2 reveals that the [V₄O₁₂]^4- anions adopt chair-like and boat-like configurations respectively, and are coordinated to each Cu(II) ions through a single terminal oxygen atom of two cross vanadium sites. Moreover, Complexes 1 and 2 exhibit trans- and cis-configurations, respectively.