Wen-Shu Hwang

Structural, photophysical, and catalytic properties of Au(I) complexes with 4-substituted pyridines.

Ionic gold(I) complexes with general formula of [Au(Py)2][AuCl2] and [Au(Py)2][PF6] (Py = 4-substituted pyridines) have been synthesized. Structures of five Au(I) complexes and a Ag(I) complex were determined by single crystal X-ray diffraction. Evidence for cationic aggregation of [Au(py)2][PF6] complexes in solution was obtained by conductivity measurements and by the isosbestic point observed from variable temperature UV-visible absorption spectra. All compounds were luminous in the solid state. Calculations employing density functional theory were performed to shed light on the nature of the electronic transitions. While the [Au(4-dmapy)2][AuCl2] (4-dmapy = 4-dimethylaminopyridine) and [Au(4-pic)2][AuCl2] (4-pic = 4-picoline) emissions were found to be mainly ligand in nature, their [PF6](-) counterparts involved a Au...Au-interaction imbedded in the highest occupied molecular orbital. [Au(4-dmapy)2][AuCl2] was found to be an efficient catalyst for Suzuki cross-coupling of aryl bromide and phenylboronic acid.

Iron carbonyl complexes from 2-[2,3-diaza-4-(2-thienyl)buta-1,3-dienyl]thiophene: NN bond cleavage and cyclometalation

Abstract When thienyl Schiff base 1, derived from 2-formylthiophene and hydrazine, reacted with Fe2(CO)9 in n-hexane, three major complexes were obtained: (1) a diironhexacarbonyl complex with two 2-thienylmethylideneamido bridging ligands 2, which resulted from the NN bond cleavage of ligand 1; (2) a doubly cyclometalated di-μ-di-(η1:η2-thienyl; η1:η1(N))bis(hexacarbonyldiiron) complex (3); and (3) a cyclometalated (μ-η1:η2-thienyl; η1:η1(N))hexacarbonyldiiron complex (4). Molecular structures of compounds 1a, 1c, and 2a have been determined by single-crystal X-ray diffraction.

Reactions of cyclometalated carbonyliron complex derived from thienyl Schiff base

Abstract Cyclometalated hexacarbonyldiiron complex 2 , which derived from N -(2-thienylmethylidene)aniline, undergoes (1) thermolysis to recover the original Schiff base 1 , (2) reduction to form a hydrogenation product of the original thienyl Schiff base 3 , (3) substitution to form a phosphine-substituted complex 4 , and (4) chemical as well as electrochemical oxidation to produce a γ-lactam 5 .

Reaction of N-(3-methyl-2-thienylmethylidene)aniline with diiron nonacarbonyl: cyclometalation induced methyl migration, imidoyl complex formation, and hydrogenation

Abstract The reaction of N-(3-methyl-2-thienylmethylidene)aniline with Fe2(CO)9 under mild conditions in anhydrous benzene gives ironcarbonyl organometallic products 2b, 2c, 5, and an organic product 4c. Complexes 2b and 2c are cyclometalated diironhexacarbonyl isomers, in which the methyl group has migrated from β- to β′- and α′-carbon of the thienyl ring, respectively. Complex 5 is a triironnonacarbonyl cluster with an imidoyl ligand capped on the top of the three-iron plane and a hydrogen atom bridged to two irons. The organic product 4c is a hydrogenated product of the original Schiff base. Single crystals of 2c and 5 were subjected to the X-ray diffraction analysis and their structures thus confirmed.

Nitrate and perchlorate salts of a silver(I) complex from 5-methyl-2-(2,3-diaza-4-(5-methyl-2-thienyl)buta-1,3-dienyl)-thiophene

Abstract Bis(5-methyl-2-(2,3-diaza-4-(5-methyl-2-thienyl)buta-1,3-dienyl)thiophene) silver(I) complex was synthesized in high yield by refluxing 5-methyl-2-(2,3-diaza-4-(5-methyl-2-thienyl)buta-1,3-dienyl)thiophene (L) with silver nitrate or silver perchlorate in anhydrous acetonitrile. The product thus formed was well characterized by NMR, IR, UV–Vis and mass spectroscopies as well as elemental analysis and electrochemical analysis. Molecular structures of compounds L, [L2Ag]NO3 and [L2Ag]ClO4 were determined by single crystal X-ray diffraction analysis. It was found that the CN double bond of the ligand rotated during the course of ligand coordination in the case of the perchlorate salt but not in the case of the nitrate salt.

Ironcarbonyl complexes from N-(2-thienylmethylidene)benzylamines: endo as well as exo cyclometalation and alkyl exchange

Abstract The reaction of methyl substituted N-(2-thienylmethylidene)benzylamine (1) with Fe2(CO)9 in benzene gives endo cyclometalated (μ-η1:η2-thienyl; η1:η1(N))hexacarbonyldiiron complexes (2 and 5), exo cyclometalated (μ-η1:η2-phenyl; η1:η1(N))hexacarbonyldiiron complexes (3 and 6) and/or imidoyl triironnonacarbonyl cluster (4), in accordance with the position of methyl substituent(s). In complex 3, the thienyl unit of the original Schiff base has been replaced by a phenyl group, which comes from the same Schiff base. The X-ray structure analyses were carried out on complexes 2a, 2b, 2c and 3a.

Photofunctional Platinum Complexes Featuring N‐heterocyclic Carbene‐Based Pincer Ligands

Photoactive platinum complexes of stoichiometry [Pt((R)CCC(R))L](0/+) (R = Me, nBu and L = -CN, -C≡CPh, -N≡CCH3, -Py, -CO) featuring pincer-type bis N-heterocyclic carbene (NHC) ligands ((R)CCC(R)) were synthesized. Organometallic syntheses of these complexes are facile and achievable through standard laboratory procedures. Control of intermolecular Pt⋅⋅⋅Pt interaction, π-π stacking, and emission tuning is achieved through suitable choice of the NHC-wingtip substituent (R) and the auxiliary ligand (L). Exposure to specific volatile organic compounds (VOCs) or mechanical grinding triggers changes in emission colors, which render these complexes photofunctional. Solid-state structures and photoluminescence results are described herein.

A new Cu(II) bridging-carboxylate helical chain polymer : synthesis and structural aspects

The crystal structure of a new Cu(II) carboxylato-bridged complex [Cu(L)(SCN)]n (1) [where HL = 2-N-(2′-pyridylimine)benzoic acid] forms a helical chain polymer chain. In 1, adjacent copper atoms are linked by carboxylate groups in a syn–anti conformation. The title complex was also characterised by elemental analysis, IR spectra, electronic spectra and variable temperature magnetic measurements.

Cytotoxic potency of self-assembled Ruthenium(II)-NHC complexes with pincer type 2, 6-bis(N-methylimidazolylidene/benzimidazolylidene)pyrazine ligands.

OBJECTIVE To study the cytotoxic potency of self-assembled Ruthenium(II)-NHC complexes with 2,6-di-(N-methylimidazolylidene/benzimidazolylidene)pyrazine ligands. MATERIALS AND METHODS Ru(II)-N-heterocyclic (Ru-NHC) complexes, Bis-[2,6-di-(N-methylimidazol-2-ylidene)pyrazine]ruthenium(II) hexaflurophosphate (3), Bis-[2,6-di-(N-methylbenzimidazol-2-ylidene)pyrazine]ruthenium(II) hexaflurophosphate (4) have been synthesized from corresponding ligands 2,6-di-(N-methylimidazolium)pyrazine dichloride (1); 2,6-di-(N-methylbenzimidazolium)pyrazine dichloride (2). Complexes were studied to determine their pro-apoptotic activity against HCT15 and Hep2 cell lines, and antimicrobial activity against Pseudomonas aeruginosa, Staphylococcus epidermidis and Candida albicans. RESULTS Both, complex 3 and 4, formed a nanosphere structure in aqueous growth medium. Cytotoxicity study revealed that complex 3 was more effective than complex 4. Complexes mainly target cellular DNA and bacterial cell wall. CONCLUSION This is the first report on the formation of nanoball structure of Ru(II)-NHC complexes. Thus, complex 3 provides a new insight to develop antitumor or antimicrobial drug.

N-(2-Chloro­quinolin-3-ylmethyl­ene)aniline

The title compound, C16H11ClN2, displays a trans configuration across the C=N bond and a transoid arrangement across the quinoline ring and the azomethine C atom. This arrangement facilitates C—H⋯Cl interactions. The packing in the crystal structure is due to intermolecular C—H⋯π and Cl⋯π (3.52 and 3.84 Å) interactions. The dihedral angle between the least-squares planes of 2-chloroquinoline and phenylamine is 16.61 (2)°.