3D pillar-layered coordination polymers based on 4d–4f heterometallic assembly

By control of mixed ligands with particular coordination sites, heterometallic coordination polymers, [Ln₂(H₂O)₂Ag(C₂O₄)₂(ina)₃]_n (Ln = Eu (1), Dy (2), Hina = isonicotinic acid) and {[LnAg(C₂O₄)(na)₂]·2H₂O}_n (Ln = La (3), Tb (4), Hna = nicotinic acid), have been synthesized under hydrothermal conditions and characterized by elemental analysis, IR, thermogravimetric analysis (TGA), and single-crystal X-ray diffraction. These coordination polymers feature 3D pillar-layered coordination frameworks constructed from two-dimensional (2D) lanthanide–carboxylate layers and Ag(ina) or Ag(na) pillars. It is interesting that the in situ decarboxylation of pyridine-2,3-dicarboxylic acid into nicotinic acid was observed. The luminescent properties of 1 and 4 were also studied.     

Novel Fe (III) heterochelates: Synthesis,structural features and fluorescence studies

Fluorescence properties of five 4-acyl pyrazolone based hydrazides (H₂SB_n) and their Fe (III) heterochelates of the type [Fe(SB_n)(L)(H₂O)]·mH₂O [H₂SB_n = nicotinic acid [1-(3-methyl-5-oxo-1-phenyl-4,5-di hydro-1H-pyrazol-4yl)-acylidene]-hydrazide; where acyl = –CH₃, m = 4 (H₂SB₁); –C₆H₅, m = 2 (H₂SB₂); –CH₂–CH₃, m = 3 (H₂SB₃); –CH₂–CH₂–CH₃, m = 1.5 (H₂SB₄); –CH₂–C₆H₅, m = 1.5 (H₂SB₅) and HL = 1-cyclopropyl-6-fluoro-4-oxo-7-(piperazin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid] were studied at room temperature. The fluorescence spectra of heterochelates show red shift, which may be due to the chelation by the ligands to the metal ion. It enhances ligand ability to accept electrons and decreases the electron transition energy. The kinetic parameters such as order of reaction (n), energy of activation (E_a), entropy (S*), pre-exponential factor (A), enthalpy (H*) and Gibbs free energy (G*) have been reported.     

Luminescent coordination polymers with extended Au(I)–Ag(I) interactions supported by a pyridyl-substituted NHC ligand

Reaction of [Ag(CH₃impy)₂]PF₆, 1, with Au(tht)Cl produces the monometallic Au(I)-species [Au(CH₃impy)₂]PF₆, 2. Treatment of 2 with excess AgBF₄ in acetonitrile, benzonitrile or benzylnitrile produces the polymeric species {[AuAg(CH₃impy)₂(L)](BF₄)₂}_n, (L = CH₃CN,3; L = C₆H₅CN, 4; L = C₆H₅CH₂CN, 5) where the Au(I) centers remain bound to two carbene moieties while the Ag(I) centers are coordinated to two alternating pyridyl groups and a solvent molecule (L). Reaction of 2 with AgNO₃ in acetonitrile produces the zig-zag mixed-metal polymer {[AuAg(CH₃impy)₂(NO₃)]NO₃}_n, 6, that contains a coordinated nitrate ion in place of the coordinated solvent species. All of these polymeric materials are dynamic in solution and dissociate into their respective monometallic components. Compounds 2–6 are intensely luminescent in the solid-state and in frozen solution. All of these complexes were characterized by ¹H, ¹³C NMR, electronic absorption and emission spectroscopy and elemental analysis.     

Helicity-induced two-layered Cd(II) coordination polymers built with different kinked dicarboxylates and an organodiimidazole

A new ligand bis-(4-imidazol-1-yl-phenyl)-diazene (azim), incorporating an azo moiety at the center and two imidazole groups at the terminals has been designed and synthesized. Under solvothermal conditions, this ligand reacts with Cd(NO₃)₂·6H₂O and different angular aromatic dicarboxylates to form layered coordination polymers: [Cd(azim)(bcp)]_n (1) and {[Cd(azim)(oba)](H₂O)}_n (2) [bcpH₂ = 1,3-bis-(4′-carboxy phenoxy)benzene; oba = 4,4′-oxybis(benzoate)]. Both 1 and 2 have been characterized by single-crystal X-ray diffraction technique, elemental analysis, PXRD and IR spectroscopy. The structure of each polymer looks like 2D grid where two layers are interpenetrated in a “cloth-like” topology. Both the structures contain single- and double-stranded helical coils where the pitches as well as the width are controlled by the carboxylate co-ligands. The hydrogen-bonding interactions between adjacent layers extend these structures to overall 3D supramolecular architectures.     

Synthesis of palladium–biscarbene complexes derived from 1,1′-methylenebis(1,2,4-triazole) functionalized in the methylene bridge

Palladium–biscarbene complexes derived from N,N′-bis(1,2,4-triazol-1-yl)methane, which bear an alkyl chain functionalized with a hydroxyl group, have been synthesized ([Pd(L1)Br₂] (6) and [Pd(L1)I₂] (7) [L1 = 1,1′-(3-hydroxypropylidene)bis(4-butyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene)]). Each product is obtained as a non-equimolecular mixture of two conformers. The hydroxyl group has been replaced by bromide and methanesulphonate and ( [Pd(L2)Br₂] [L2 = 1,1′-(3-bromopropylidene)bis(4-butyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene)] (9)) and ([Pd(L3)Br₂] [L3 = 1,1′-(3-methanesulphonyloxypropylidene)-bis(4-butyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene)] (10)) were obtained, respectively, as mixtures of conformers. All compounds consist of a six-membered metallacyclic structure in a boat conformation. Major conformers present the functionalized chain in the axial position, while in minor conformers it is located in the equatorial position.     

Gas phase synthesis and X-ray crystal structures of supramolecular networks with bromocorannulene: Similarities and differences with their corannulene analogs

The reactivity of bowl-shaped mono-bromocorannulene (C₂₀H₉Br) has been examined and compared with that of corannulene (C₂₀H₁₀). Although bromination of corannulene was shown to flatten the bowl and change its electronic properties, it has not affected the outcome of coordination reactions toward the avid Lewis acidic [Rh₂(O₂CCF₃)₄] complex. Two new products have the same composition [{Rh₂(O₂CCF₃)₄}_m · (C₂₀H₉Br)_n] where m:n = 1:1 (1) and 3:2 (2), as the corresponding corannulene-based analogs. The X-ray diffraction studies of 1 and 2 revealed 1D chain and 2D layered structures built on η²-coordination of rhodium(II) to rim carbon sites of the C₂₀H₉Br-bowl, similar to those of C₂₀H₁₀. While no essential difference is found in 2D structures, the local coordination environments of the [Rh₂(O₂CCF₃)₄] unit differ in their 1D complexes.     

Construction of Cd(II)–ferrocenesuccinate coordination complexes via changing adjuvant ligands and anions

Seven Cd(II)–ferrocenesuccinate coordination complexes with the formulas [Cd(η²-FcCOC₂H₄COO)₂(pbbbm)]₂ (1), [Cd(η²-FcCOC₂H₄COO)(pbbbm)Cl]₂ (2), [Cd(η²-FcCOC₂H₄COO)(pbbbm)I]₂ (3), {[Cd(η²-FcCOC₂H₄COO)₂(btx)₂]₂(CH₃OH)_0.5} (4), [Cd(η²-FcCOC₂H₄COO)₂(bix)]₂(H₂O) (5), {[Cd(η²-FcCOC₂H₄COO)(bbbm)_1.5Cl] · (CH₃OH)_0.5}_n (6), and {[Cd(η²-FcCOC₂H₄COO)(mbbbm)Cl] · (H₂O)_2.75}_n (7) [pbbbm = 1,4-Bis(benzimidazole-1-ylmethyl)benzene), btx = 1,4-bis(triazol-1-ylmethyl)benzene), mbbbm = 1,3-bis(benzimidazole-1-ylmethyl)benzene), bix = 1,4-bis(imidazol-1-ylmethyl)benzene, bbbm = 1,1-(1,4-Butanediyl)bis-1H-benzimidazole)] have been synthesized and characterized. Single-crystal X-ray analysis reveals that complexes 1–5 are all dimers and bridged by pbbbm, btx and bix, respectively. But the five complexes present some differences in their dimeric conformations, which can be ascribed to the impacts of adjuvant ligands and counter anions. In contrast to complexes 1–5, both 6 and 7 are of 1-D structures (with the same counter anions), and the former is double ladder-like structure only bridged by bbbm, while the latter is chain-like structure bridged by chlorine anions and adjuvant ligand mbbbm. Notably, various π–π interactions are found in complexes 1–7, and they have significant contributions to molecular self-assembly processes. The electrochemical studies of complexes 1–7 in DMF solution display irreversible redox waves and indicate that the half-wave potentials of the ferrocenyl moieties in these complexes are all shifted to positive potential compared with that of ferrocenesuccinate.     

Organoselenium(II) complexes containing organophosphorus ligands. Crystal and molecular structure of PhSeSP(S)Ph2, [2-{MeN(CH2CH2)2NCH2}C6H4]SeSP(S)R′2 (R′ = Ph,OPri) and [2-{O(CH2CH2)2NCH2}C6H4]SeSP(S)(OPri)2

Arylselenium(II) derivatives of dithiophosphorus ligands of type ArSeSP(S)R₂ [Ar = Ph, R = Ph (1), OPrⁱ (2); 2-[MeN(CH₂CH₂)₂NCH₂]C₆H₄, R = Ph (3), OPrⁱ (4); 2-[O(CH₂CH₂)₂NCH₂]C₆H₄, R = OPrⁱ (6)] were prepared by redistribution reactions between Ar₂Se₂ and [R₂P(S)S]₂. The derivative [2-{O(CH₂CH₂)₂NCH₂}C₆H₄]SeSP(S)Ph₂ (5) was obtained by the salt metathesis reaction between [2-{O(CH₂CH₂)₂NCH₂}C₆H₄]SeCl and NH₄S₂PPh₂. The compounds were investigated by multinuclear (¹H, ¹³C, ³¹P, ⁷⁷Se) NMR and infrared spectroscopy. The crystal and molecular structures of 1, 3, 4 and 6 were determined by single-crystal X-ray diffraction. In compounds 3, 4 and 6 the N(1) atom is intramolecularly coordinated to the selenium center, resulting in a T-shaped geometry (hypervalent 10-Se-3 species). The dithiophosphorus ligands act as anisobidentate in 1 and monodentate in 3, 4 and 6. Supramolecular architectures based on intermolecular S?H and N?H contacts between molecular units are formed in the hypervalent derivatives 3 and 4, while in the compounds 1 and 6 the molecules are associated into polymeric chains through either Se?S or O?H contacts, with no further inter-chain interactions.     

Synthesis and characterization of thiosemicarbazone derivatives of 2-chloro-4-hydroxy-benzaldehyde and their rhenium(I) complexes

N-Thioamide thiosemicarbazone derived of 2-chloro-4-hydroxy-benzaldehyde (R = H, HL¹; R = Me, HL² and R = Ph, HL³) have been prepared and their reaction with fac-[ReX(CO)₃(CH₃CN)₂] (X = Br, Cl) in chloroform gave the adducts [ReX(CO)₃(HL)] (1a X = Cl, R = H; 1a′ X = Br, R = H; 1b X = Cl, R = CH₃; 1b′ X = Br, R = CH₃; 1c X = Cl, R = Ph; 1c′ X = Br, R = Ph) in good yield. Complexes 1a′ and 1b’ were also obtained by the reaction of HL¹ and HL³ with [ReBr(CO)₅] in toluene.All the compounds have been characterized by elemental analysis, mass spectrometry (FAB), IR and ¹H NMR spectroscopic methods. Moreover, the structures of HL², HL³ and 1a·H₂O were also established by X-ray diffraction. In 1a, the rhenium atom is coordinated by the sulphur and the azomethine nitrogen atoms, forming a five-membered chelate ring, as well as three carbonyl carbon and chloride atoms. The resulting coordination polyhedron can be described as a distorted octahedron.The study of the crystals obtained by slow evaporation of methanol and DMSO solutions of the adducts 1a′ and 1b, respectively, showed the formation of dimer structures based on rhenium(I) thiosemicarbazonates [Re₂(L¹)₂(CO)₆]·3H₂O (2a)·3H₂O and [Re₂(L²)₂(CO)₆]·(CH₃)₂SO (2b)·2(CH₃)₂SO. Amounts of these thiosemicarbazonate complexes [Re₂(L)₂(CO)₆] (2) were obtained by reaction of the corresponding free ligands with [ReCl(CO)₅] in dry toluene.In 2a·3H₂O and 2b·2(CH₃)₂SO the dimer structures are established by Re–S–Re bridges, where S is the thiolate sulphur from a N,S-bidentate thiosemicarbazonate ligand. In both structures the rhenium coordination sphere is similar; the dimers are in the same diamond Re₂S₂ face.     

Self-assembly of zinc polymers based on a flexible linear ligand at different pH values: Syntheses,structures and fluorescent properties

Five novel coordination polymers, [Zn(imbz)₂]_n (1), {[Zn(imbz)₂]·H₂O}_n (2), [Zn(imbz)(μ₂-OH)]_n (3), [Zn₃(imbt)₂(p-bdc)₃]_n (4), [Zn₄(μ₃-OH)₂(imbt)₂(p-bdc)₃]_n (5), (imbt = 4′-(imidazol-1-ylmethyl)benzonitrile, imbz^? = 4′-(imidazol-1-ylmethyl)benzoate and p-bdc = terephthalic acid) have been hydrothermally prepared through systematically changing the pH values of reaction mixture, and structurally characterized by elemental analysis, IR spectroscopy and single-crystal X-ray crystallography. Compounds 1 and 2 exhibit similar 2D (4,4) grid structures, whereas compound 2 contains a right-handed helix along b-axis. Compound 3 has a distorted diamond framework which was constructed via imbz^? ligands and μ₂-OH groups linking metal atoms. Compound 4 shows a 2D 6-connected network with trinuclear zinc clusters as secondary building units (SBUs), whereas 5 shows a distorted α-Po with tetranuclear zinc clusters as SBUs, in which p-bdc ligands act as bridges. Moreover, compounds 1–5 all exhibit strong blue photoluminescence in the solid state at room temperature.     

Synthesis and characterization of novel five-membered palladacycles

3-(2-Chloroquinolin-3-yl)-1,5-bis(3,4,5-trimethoxy-phenyl)-pentane-2,4-dione derivatives 3a–b were conveniently synthesized in excellent yields (82% each) by tandem Knoevenagel condensation reactions of 2-chloro-3-carbaldehyde-quinoline 1a–b with 3,4,5-trimethoxy acetophenone, followed by a base catalyzed Michael addition, such as DBU (1,8-diazabicyclo[5,4,0]undec-7-ene) with or without solvent. The reactions of 3a–b with Pd(dba)₂ in the presence of PPh₃ (1:2) in degassed acetone provided the dinuclear palladium complexes {Pd(C,N-2-C₉H₄N–CH–[–CH₂CO(3,4,5-(OMe-)₃–C₆H₂-]₂–3-R-6)Cl(PPh₃)}₂ [(R = H (4a), R = OMe (4b)] in moderate yields (38% and 43%), which in turn reacted with an excess of isonitrile XyNC (Xy = 2,6-Me₂C₆H₃) to give the corresponding palladacycles 5a–b in moderate yields (45% and 43%). The palladacycles 5a–b were also obtained in similar yields (32% and 33%) via a one-pot oxidative addition reaction of 3a-b with isonitrile XyNC:Pd(dba)₂ (4:1). The products were characterized by satisfactory elemental analysis and spectral studies (IR, ¹H, and ³¹P NMR). The crystal structure of 5a was determined by X-ray crystallography diffraction studies.     

Synthesis,characterization and NLO properties of a new 3D coordination polymer assembled from p-aminobenzoic acid

Reaction of Zn(NO₃)₂·6H₂O with p-aminobenzoic acid in a 1:2 molar ratio under ethanol medium at room temperature affords a new three dimensional (3D) coordination polymer [Zn(PABA)₂]·H₂O (1) (PABA = p-aminobenzoic acid). Single-crystal X-ray diffraction reveals that 1 crystallizes in the orthorhombic system, space group P2₁2₁2₁, a = 7.614(2), b = 11.133(3), c = 16.869(4). 1 adopts a 3D open framework with H₂O molecules in the cavities. PABA, acting as bridging ligand as well as coordinating ligand, adopts a different coordination mode to bridge Zn atoms and form the 3D supramolecular structure which is further stabilized by N–H?O, O–H?O hydrogen bonding and π–π stacking interactions. Powder second-harmonic generation (SHG) efficiency measurement with Nd:YAG laser (1064 nm) radiation shows that the SHG efficiency of 1 is equivalent to KDP crystal. The present work also demonstrates that the framework of 1 is retained after removal of the guest H₂O molecules, and the H₂O molecules can be reintroduced into the framework, indicating that this complex may also be used to generate porous materials.     

Copper(I) complexes of heterocyclic thiourea ligands

The coordination of heterocyclic thiourea ligands (L = N-(2-pyridyl)-N′-phenylthiourea (1), N-(2-pyridyl)-N′-methylthiourea (2), N-(3-pyridyl)-N′-phenylthiourea (3), N-(3-pyridyl)-N′-methylthiourea (4), N-(4-pyridyl)-N′-phenylthiourea (5), N-(2-pyrimidyl)-N′-phenylthiourea (6), N-(2-pyrimidyl)-N′-methylthiourea (7), N-(2-thiazolyl)-N′-methylthiourea (8), N-(2-benzothiazolyl)-N′-methylthiourea (9), N,N′-bis(2-pyridyl)thiourea (10) and N,N′-bis(3-pyridyl)thiourea (11)) with CuX (X = Cl, Br, I, NO₃) has been investigated. CuX:L product stoichiometries of 1:1–1:5 were found, with 1:1 being most common. X-ray structures of four 3-coordinate mononuclear CuXL₂ complexes (CuCl(6)₂, CuCl(7)₂, CuBr(6)₂, and CuBr(9)₂) are reported. In contrast, CuBr(1)₂ is a 1D sulfur-bridged polymer. CuIL structures (L = 7, 8) are 1D chains with corner-sharing Cu₂(μ-I)₂ and Cu₂(μ-S)₂ units, and CuCl(10) is a 2D network having μ-Cl and N-/S-bridging L. Two [CuL₂]NO₃ structures are reported: a mononuclear 4-coordinate copper complex with chelating ligands (L = 10) and a 1D link-chain with N-/S-bridging L (L = 3). Two ligand oxidative cyclizations were encountered during crystallization. CuI crystallized with 6 to produce zigzag ladder polymer [(CuI)₂(12)]·½CH₃CN (12 = N-(pyrimidin-2-yl)benzo[d]thiazol-2-amine) and CuNO₃ crystallized with 10 to form [Cu₂(NO₃)(13)₂(MeCN)]NO₃ (13 = dipyridyltetraazathiapentalene).     

Conformational and stereoelectronic investigation of chloromethyl methyl sulfide and its sulfinyl and sulfonyl analogs

Three compounds based on polyoxometalate building blocks, [Cu(en)₂]{[Cu(en)₂]₂[Mo^VI₅Mo^V₃V^IV₈O₄₀(PO₄)]} · 4H₂O (1), [Co(en)₂]{[Co(en)₂]₂[HMo^VI₄Mo^V₄V^IV₈O₄₀(PO₄)]} · 5H₂O (2) and [Ni(en)₂]{[Ni(en)₂]₂[Mo^VI₅Mo^V₃V^IV₈O₄₀(VO₄)]} · 2H₂O (3) (en = ethylenediamine), have been synthesized and characterized by elemental analysis, IR, XPS, XRD, TGA and single-crystal X-ray diffraction analysis. The result of structure determination shows that isomorphic compounds 1, 2 and 3 feature a one-dimensional chain built from the reduced tetra-capped pseudo-Keggin polyoxoanion, which is further interconnected by [M(en)₂]²⁺ (M = Cu, Co and Ni) groups via the terminal oxygen atoms of polyoxoanions. The crystal data for these compounds are the following: 1, monoclinic, space group C2/c, a = 26.702(3) Å, b = 13.4539(14) Å, c = 19.5987(19) Å, β = 108.650(2)°, V = 6671.0(12) Å³, Z = 4; 2, monoclinic, space group C2/c, a = 26.244(3) Å, b = 13.5070(17) Å, c = 19.581(3) Å, β = 106.881(2)°, V = 6641.8(15) Å³, Z = 4; 3, monoclinic, space group C2/c, a = 26.2789(15) Å, b = 13.5408(6) Å, c = 19.6312(9) Å, β = 106.2590(10)°, V = 6706.1(6) Å³, Z = 4. Variable-temperature magnetic susceptibility measurements of compounds 1 and 3 reveal the feature of antiferromagnetic exchange in these compounds.     

Metal complexes of tetradentate and pentadentate N-o-hydroxybenzamido-meso-tetraphenylporphyrin ligand: M(N-NCO(o-OH)C6H4-tpp) (M = Zn2+, Ni2+, Cu2+) and M′(N-NCO(o-O) C6H4-tpp) (M′ = Mn3+) (tpp = 5, 10, 15, 20-tetraphenylporphyrinate)

The crystal structures of N-o-hydroxybenzimido-meso-tetraphenylporphyrinatozinc(II) toluene solvate [Zn(N-NCO(o-OH)C₆H₄-tpp)·C₆H₅CH₃; 4·C₆H₅CH₃], N-o-hydroxybenzimido-meso-tetraphenylporphyrinatonickel(II) chloroform solvate [Ni(N-NCO(o-OH)C₆H₄-tpp)·0.6CHCl₃; 5·0.6 CHCl₃], N-o-hydroxybenzimido-meso-tetraphenylporphyrinatocopper(II) toluene solvate [Cu(N-NCO(o-OH)C₆H₄-tpp)·C₆H₅CH₃; 6·C₆H₅CH₃] and N-o-oxido-benzimido-meso-tetraphenylporphyrinato(-κ⁴,N¹,N²,N³,N⁵,κO²) manganese (III) methylene chloride·methanol solvate [Mn(N-NCO(o-O)C₆H₄-tpp)·CH₂Cl₂·MeOH; 8·CH₂Cl₂·MeOH] were established. The coordination sphere around Zn²⁺ ion in 4·C₆H₅CH₃, (or Ni²⁺ ion in 5·0.6 CHCl₃ or Cu²⁺ ion in 6·C₆H₅CH₃) is a distorted square planar (DSP) whereas for Mn³⁺ in 8·CH₂Cl₂·MeOH, it is a distorted trigonal bipyramid (DTBP) with O(1), N(1) and N(3) lying in the equatorial plane for 8·CH₂Cl₂·MeOH. The g value of 8.27 measured from the parallel polarization of X-band EPR spectra at 293 K is consistent with the high-spin mononuclear manganese(III) (S = 2) in 8. The magnitude of axial (D) zero-field splitting (ZFS) for the mononuclear Mn(III) in 8 was determined approximately as 3.0 cm^?1 by the paramagnetic susceptibility measurements and conventional EPR spectroscopy.     

Synthesis,structure and magnetic properties of an iron(II) complex with nitronyl nitroxides

An iron(II) complex with nitronyl nitroxides, [Fe^II(dppNN)₂](BF₄)₂ · CH₃COCH₃ (1) (dppNN = 2,6-di(pyrazol-1-yl)-4-(4,4,5,5-tetramethyl-1-oxido-3-ylooxy-4,5-dihydro-3H-imidazol-2′-yl)pyridine) was synthesized. In 1 the central iron(II) ion was coordinated by two tridentate ligands with nitronyl nitroxides. Magnetic susceptibility measurements showed that χ_mT values below 130 K was almost temperature independent, while upon increasing temperature χ_mT values showed gradual increase, suggesting an occurrence of a spin transition from low to high spin state. Green light irradiation on powder sample at 5 K resulted in spin conversion (LIESST).     

Synthesis,characterization and property study of new coordination polymers constructed from flexible dicarboxylates and bidentate nitrogen mixed ligands

Five new coordination polymers, [Cd(1,2′-cy)_0.5(bix)H₂O]_n (1), [Cd₂(1,2′-cy)₂(1,10′-phen)₂(H₂O)₂] (2), {[Co(1,2-cy)(2,2′-bipy)(H₂O)₂]·2H₂O}_n (3) {[Cd(succ)(1,10′-phen)H₂O]·H₂O}_n (4), and {[Cd(succ)(2,2′-bipy)H₂O]·2H₂O}_n (5) (1,2-cy = 4-cyclohexene-1,2-dicarboxylate, succ = succinic acid, bix = 1,4-bis(imidazol-1-ylmethyl)benzene, 1,10′-phen = 1,10-phenanthroline, 2,2′-bipy = 2,2′-bipyridine), have been synthesized and characterized by single-crystallographic X-ray diffraction. Complex 1 shows a two-dimensional covalent layer structure. Complex 2 exhibits a two-dimensional supramolecular layer network composed from discrete fundamental units. Complex 3 exhibits a one-dimensional covalent chain-like structure, which further extends to a two-dimensional supramolecular structure with hydrogen bonding and π-π interactions respectively. Complexes 4 and 5 show three-dimensional supramolecular networks composed from one-dimensional chain-like covalent structures. Furthermore, the magnetic property of complex 3 and fluorescent properties of complexes 1, 2, 4 and 5 have also been studied.     

Dinuclear ruthenium(I) complexes of the type [Ru2(CO)4L2] with carboxylate or 2-pyridonate ligands: Evaluation as catalysts for olefin cyclopropanation with diazoacetates

Dinuclear ruthenium(I,I) carboxylate complexes [Ru₂(CO)₄(μ-OOCR)₂]_n (R = CH₃ (1a), C₃H₇ (1b), H (1c), CF₃ (1d)) and 2-pyridonate complex [Ru₂(CO)₄(μ-2-pyridonate)₂]_n (3) catalyze efficiently the cyclopropanation of alkenes with methyl diazoacetate. High yields are obtained with terminal nucleophilic alkenes (styrene, ethyl vinyl ether, α-methylstyrene), medium yields with 1-hexene, cyclohexene, 4,5-dihydrofuran and 2-methyl-2-butene. The E-selectivity of the cyclopropanes obtained from the monosubstituted alkenes and the cycloalkenes decreases in the order 1b > 1a > 1d > 1c. The cyclopropanation of 2-methyl-2-butene is highly syn-selective. Several complexes of the type [Ru₂(CO)₄(μ-L¹)₂]₂ (4) and (5), [Ru₂(CO)₄(μ-L¹)₂L²] (L² = CH₃OH, PPh₃) (6)–(9) and [Ru₂(CO)₄(CH₃CN)₂(μ-L¹)₂] (10) and (11), where L¹ is a 6-chloro- or 6-bromo-2-pyridonate ligand, are also efficient catalysts. Compared with catalyst 3, a halogen substituent at the pyridonate ligand affects the diastereoselectivity of cyclopropanation only slightly.     

Synthesis,characterization and cytotoxic investigations of novel bis(indole) analogues besides antimicrobial study

Two series of novel bis(indole) analogues viz., N′-((5-substituted-1H-indol-3-yl)methylene)-n-(1H-indol-3-yl)alkanehydrazides (7a–f) and N′-((5-substituted-1-(3-methylbut-2-enyl)-1H-indol-3-yl)methylene)-n-(1H-indol-3-yl)acetohydrazide (8a–f) were synthesized and characterized by spectral analysis. The target molecules were screened for their antimicrobial, anticancer activities and structure and activity relationship (SAR) was investigated. Compounds 7a, 7c and 8a were found to be active in antimicrobial screening. Anticancer screening reveals that Compound 7c was active against HeLa cell line with an IC₅₀ of 43.1 μM and compound 7d was found to be interesting candidate with an IC₅₀ of 26.0 and 30.2 μM against Colo-205 and Hep G2 cell lines respectively.     

Diiron chelate complexes relevant to the active site of the iron-only hydrogenase

A novel unsymmetrically disubstituted propanedithiolate compound [Fe₂(CO)₄(κ²-dmpe)(μ-pdt)] (1) (pdt = SCH₂CH₂CH₂S, dmpe = Me₂PCH₂CH₂PMe₂) was synthesized by treatment of [Fe₂(CO)₆(μ-pdt)] with dmpe in refluxing THF. Compound 1 was characterized by single-crystal X-ray diffraction analysis. Protonation of 1 with HBF₄·Et₂O in CH₂Cl₂ gave at room temperature the μ-hydrido derivative [Fe₂(CO)₄(κ²-dmpe)(μ-pdt)(μ-H)](BF₄)] (2). At low temperature, ¹H and ³¹P–{¹H} NMR monitoring revealed the formation of a terminal hydride intermediate 3. Comparison of these results with those of a VT NMR study of the protonation of symmetrical compounds [Fe₂(CO)₄L₂(μ-pdt)] [L = PMe₃, P(OMe)₃] suggests that in disubstituted bimetallic complexes [Fe₂(CO)₄L₂(μ-pdt)], dissymmetry of the complex is required to observe terminal hydride species. Attempts to extend the series of chelate compounds [Fe₂(CO)₄(κ²-L₂)(μ-pdt)] by using arphos (arphos = Ph₂AsCH₂CH₂PPh₂) were unsuccessful. Only mono- and disubstituted derivatives [Fe₂(CO)_6−n(Ph₂AsCH₂CH₂PPh₂)_n(μ-pdt)] (n = 1, 4a; n = 2, 4b), featuring dangling arphos, were isolated under the same reaction conditions of formation of 1. Compound 4b was structurally characterized.