Synthesis and physicochemical properties of fac-[Re(CO)3([kappa]2-N,N-dpkfah)Cl], dpkfah=di-2-pyridyl ketone 2-furoic acid hydrazone: the molecular structure of fac-[Re(CO)3([kappa]2-N,N-dpkfah)Cl] · acetone

• Published in: Journal of coordination chemistry Vol. 64; no. 10; p. 1743
• Main Authors: Bakir, Mohammed, Gyles, Colin
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis Ltd 01-05-2011
• Subjects: Absorption spectra; Acetone; Acids; Cadmium; Charge transfer; Crystal structure; Furoic acid; Hydrazones; Hydrogen bonds; Molecular chains; Molecular structure; NMR; Nuclear magnetic resonance; Optical measurement; Organic chemistry; Protonation; Refluxing; Single crystals; Solvents; Spectrum analysis; Structural analysis; Temperature dependence; Toluene
• ISSN: 0095-8972; 1029-0389
• DOI: 10.1080/00958972.2011.583645

Reaction between [Re(CO)5Cl] and di-2-pyridyl ketone 2-furoic acid hydrazone (dpkfah) (1) in refluxing toluene gave fac-[Re(CO)3(κ2-N,N-dpkfah)Cl] (2). Spectroscopic and electrochemical measurements disclosed sensitivity of 2 to its surroundings. 1H-NMR measurements showed that the amide proton exchanged with solvent protons, and its chemical shift is solvent and temperature dependent, while the chemical shifts of aromatic protons are solvent and temperature independent. Electronic absorption spectra of 2 divulged two intra-ligand charge transfer transitions (ILCT) in protophilic solvents and a single ILCT transition in non-protophilic solvents. Optical measurements on protophilic solutions of 2 established an equilibrium between 2 and its conjugate base, fac-[Re(CO)3(κ2-N,N-dpkfah-H)Cl]- (3). Thermo-optical measurements confirmed that the interconversion between 2 and 3 and gave [Delta]G ø values of -26.48 and 22.99 kJ mol-1, respectively, for the protonation of DMF and DMSO by 2. Optosensing measurements showed that [MCl2] (M = Zn, Cd, or Hg) in concentrations as low as 1.00 × 10-7 mol L-1 can be detected and determined using protophilic solutions of 2. Electrochemical measurements showed 2 to be more stable in CH3CN than DMF. Single-crystal X-ray structural analysis on fac-[Re(CO)3(κ2-N,N-dpkfah)Cl] · acetone (4) obtained from an acetone solution of 2 confirmed the solvent-complex interaction and revealed two symmetry-independent molecules in the asymmetric unit. The extended structure of 4 disclosed parallel stacks connected via a network of classic and non-classic hydrogen bonds.