Bei-Sheng Kang

Recent Advances in Supramolecular Design and Assembly of Silver(I) Coordination Polymers

The supramolecular chemistry of Ag(i) coordination assemblies continues to attract attention due to their versatile structural diversity and potential physical and chemical functions. This article provides a short review of recent advances in the design and construction of Ag(i) coordination polymers with special emphasis on the Ag(i) ion coordination geometry, ligand functionality, and supramolecular interactions. The potential functions of Ag(i) coordination polymers are briefly summarized.

Discrete and infinite 1D, 2D/3D cage frameworks with inclusion of anionic species and anion-exchange reactions of Ag3L2 type receptor with tetrahedral and octahedral anions

Complexes [PF6 subset(Ag3(titmb)2](PF6)2 (8) and {SbF6 subset[Ag3(titmb)2](SbF6)2}.H2O.1.5 CH3OH (9) are obtained by reaction of titmb and Ag+ salts with different anions (PF6(-) and SbF6(-)), and crystal structures reveal that they are both M3L2 cage complexes with short Ag...F interactions between the silver atoms and the fluorine atoms of the anions. In complex 8, a novel cage dimer is formed by weak Ag...F contacts; an unique cage tetramer formed via Ag...pi interactions (Ag...eta5-imidazole) between dimers and an infinite 1D cage chain is presented. However, each of the external non-disordered SbF6(-) anions connect with six cage 9s via Ag...F contacts, and each cage 9 in turn connects with three SbF6(-) anions to form a 2D network cage layer; and the layers are connected by pi-pi interactions to form a 3D network. The anion-exchange reactions of four Ag3L2 type complexes ([BF4 subset(Ag3(titmb)2](BF4)2 (6), [ClO4 subset(Ag3(titmb)2](ClO4)2 (7b), [PF6 subset(Ag3(titmb)2](PF6)2 (8) and [SbF6 subset(Ag3(titmb)2](SbF6)2.1.5CH3OH (9)) with tetrahedral and octahedral anions (ClO4(-), BF4(-), PF6(-) and SbF6(-)) are also reported. The anion-exchange experiments demonstrate that the anion selective order is SbF6(-) > PF6(-) > BF4(-), ClO4(-), and this anion receptor is preferred to trap octahedral and tetrahedral anions rather than linear or triangle anions; SbF6(-) is the biggest and most preferable one, so far. The dimensions of cage complexes with or without internal anions, anion-exchange reactions, cage assembly and anion inclusions, silver(I) coordination environments, Ag-F and Ag-pi interactions of Ag3L2 complexes 1-9 are discussed.

Chair-form [Ag2(1,2-bimb)2]2+ in silver(I) complexes containing the ditopic ligand 1,2-bis(1-imidazolylmethyl)benzene (1,2-bimb)

Abstract The ditopic ligand 1,2-bis(1-imidazolylmethyl)benzene (1,2-bimb) and its silver(I) complexes [Ag2(1,2-bimb)2](PF6)2 (1) and {[Ag2(1,2-bimb)2]2(SbF6)4}n (2) were prepared and their structures characterized by X-ray crystallography. Both complexes contain the chair-form unit [Ag2(1,2-bimb)2]2+ with Ag(I) linearly coordinated by NIm (Im=1-imidazolyl) from the Im groups of two 1,2-bimb. However, the [Ag2(1,2-bimb)2]2+ units are positioned differently in forming 1D infinite chains through weak argentophilic interactions: linear chains in 1 with the units oriented in same direction are formed via Ag⋯π interactions, while polymeric chains constructed via Ag⋯Ag interactions in 2 are observed with the units arranged in alternate directions. Differences in supramolecular structures may be a result of different size of the anions.

Partially cyclopentadienyl-substituted tetranuclear lanthanide Schiff base complexes

Treatment of Cp 3 Ln (Ln=Pr, Nd) with an equimolar amount of the Schiff base bis(acetylacetone)ethylenediamine (H 2 acacen) half hydrate (H 2 L 1 ·1/2H 2 O) or bis(salicylidene)trimethylenediamine (H 2 saltn) half hydrate (H 2 L 2 ·1/2H 2 O) in THF affords three novel μ-hydroxo-bridged tetranuclear organolanthanide complexes [η 5 -CpLn 2 L 2 (μ-OH)] 2 · n THF, L=L 1 , n =4, Ln=Pr ( 1 ), Nd ( 2 ); L=L 2 , n =2, Ln=Nd ( 3 ). A reaction scheme was proposed in which the cyclopentadienyl lanthanide coordination motif [CpLnL] ( A ) and the hydroxyl lanthanide motif [LnL(OH)] ( B ) cross-reacted and then dimerized through the μ-hydroxo bridges to give the tetranuclear Ln complexes containing an Ln 4 O 8 skeleton with two reciprocally oriented face-sharing defect cubanes. In each monomeric species [CpLn 2 L 2 (OH)] ( C ) the Ln atoms are 8- or 9-coordinated. All complexes have been characterized by EA, IR and Mass spectroscopy.

Syntheses and electrochemistry of some transition metal complexes with 2-mercaptopyridine N-oxide and crystal structure of bis(2-mercaptopyridine N-oxide)nickel(II)

Abstract The complexes M(mpo)n (M = Mn, Ni, n = 2; M = Fe, Co, n = 3) (Hmpo = 2-mercaptopyridine N-oxide) were prepared by reacting the appropriate metal chloride with either Nampo or dtpo [2,2-dithiobis(pyridine N-oxide)] in the presence of sodium methoxide. The structure of the complex Ni(mpo)2 was determined by X-ray diffraction. The nickel atom is in a square planar environment of two mpo− ligands in the cis configuration. The four complexes were investigated by physicochemical methods especially by 1H NMR spectroscopy and cyclic voltammetry.

Syntheses and characterization of copper(II) complexes of bis(acetylacetone)trimethylenediimine

Abstract Copper(II) complexes [Cu(acactn)H2O]2 (1) and [Cu2(acactn)2KClO4]2 (2), where H2acactn is a tetradentate Schiff base bis(acetylacetone)trimethylenediimine, have been prepared and characterized by IR, CV and X-ray single crystal structure analyses. The ligand H2acactn is strongly metallophilic to stabilize Cu(II) ion with a square planar N2O2 coordination environment. Complex 1 can be seen as a hydrogen-bonded dimer of building block Cu(acactn) via bridging water molecules, while complex 2 is a tetrametric adduct of [Cu(acactn)] moiety and KClO4, in which K+ and ClO4− are the bridging-groups. Electrochemical studies displayed that Cu(II)/Cu(I) is an irreversible one-electron reduction process.

Modulation of the coordination environment of silver(I) in bis(diphenylphosphino)methane complexes by selection of heterocyclic thiolato ligands

Abstract Complexes [Ag 4 (mbi: N , N , S )(dppm) 4 ][BF 4 ] 2 ( 1 ), [Ag 4 (mpym: N , S ) 2 (dppm) 4 ][BF 4 ] 2 ( 2 ) and [Ag 2 (mnic: O , S )(dppm) 2 ] 2 ( 3 ) with Ag(I) in varied coordination geometries were obtained from the reactions of AgBF 4 and the heterocyclic thiolato ligands 2-mercaptobenzimidazole (H 2 mbi), 2-mercaptopyrimidine (Hmpym) and 2-mercaptonicotinic acid (H 2 mnic), respectively, with the participation of bis(diphenylphosphino)methane (dppm). The products have been characterized by elemental analyses, IR, 1 H and 31 P NMR. X-ray crystallographic analyses showed that the structures and the coordination modes are obviously modulated by the thiolato ligands used. With the diazothiolates mbi 2− and mpym − , both 1 and 2 contain two closed [Ag 2 (dppm) 2 ] units connected by the thiolates. When the carboxyl-substituted thiopyridine (H 2 mnic) was used in 3 , a new coordination mode was observed in which the thiolate mnic 2− provided an μ 3 -S to the core of M 4 (dppm) 4 resulting in a neutral complex in which the four Ag atoms are connected by four dppm ligands head-to-tail .

Chemistry of tripodal ligands. Part III.: Copper complexes of tris(benzimidazol-2-ylmethyl)amine and of its N-n-propyl derivative

Abstract The reactions of copper (I or II) salts with ligands Rntb (tris( N -alkylbenzimidazol-2-ylmethyl)amine) gave complexes [Cu(II)(ntb)Cl]Cl·3H 2 O ( 1 ), [Cu(I)(ntb)(PPh 3 )](NO 3 )·1.5H 2 O ( 2 ), [Cu(II)(Prntb)I]Cl ( 3 ) and [Cu(I)(Prntb)I] ( 4 ), depending on the reaction conditions. X-ray single crystal diffraction analyses showed the copper atom to be tetrahedrally coordinated in 2 and 4 , but square pyramidal in 1 and trigonal bipyramidal in 3 . Structural characteristics were revealed for the complexes and compared, and complex 3 was shown to be the best model compound among the four for the active center of blue copper proteins. CV studies showed the electrochemical behaviors of the complexes: 1 has two redox couples, phosphine ligation stabilizes 2 towards redox reactions, while 3 and 4 , with the same cationic formula [Cu(Prntb)I] 1+,0 have very similar complicated redox patterns, indicating the reversibility of the two species. IR and UV–Vis spectroscopic studies were also reported.

Syntheses, crystal structures and properties of Zn(II) and Cd(II) complexes derived from N-(o-nitrophenyl)-N′-(methoxycarbonyl) thiourea(H2omt) and 2,2′-bipyridine(bpy) or o-phenanthroline(phen)

Abstract The chelating properties of N-(o-nitrophenyl)-N′-(methoxycarbonyl)thiourea (H2omt) were investigated through the study of the crystal structures of Cd(Homt)2(bpy), 1, Zn(Homt)2(phen), 2 and H2omt (bpy=2,2′-bipyridine, phen=o-phenanthroline). The cadmium(II) ion in 1 is in a distorted octahedral geometry contributed by the two N atoms from bipyridine and the two S and the two deprotonated amine N atoms from two Homt groups [Cd–N(bpy)=2.329(3), Cd–N(amine)=2.360(3) and Cd–S=2.690(1) A]. The Zn(II) ion in complex 2 is four-coordinated by the two N atoms from the o-phenanthroline and the two deprotonated amine N atoms from two Homt groups in a distorted tetrahedral fashion, in which the binding of S atom to the metal is not involved [Zn–N(phen)=2.088(4), Zn–N(amine)=1.998(3) A].

Three-fold parallel interlocking of 2-D brick-wall networks showing ladder-like unsymmetrical Borromean links

Reaction of a semi-rigid ditopic ligand, N,N′-bis(4-pyridylmethyl)pyromellitic diimide (L), with HgI2 afforded the 2-D brick-wall type (6,3) networks, which interlocked in a parallel fashion to give the first example of unsymmetrical Borromean ladder links.