Spectroscopic studies and structures of trans-ruthenium(II) and ruthenium(III) bis(cyanide) complexes supported by a tetradentate macrocyclic tertiary amine ligand.
trans-[Ru(16-TMC)(C[triple bond]N)2] (1; 16-TMC = 1,5,9,13-tetramethyl-1,5,9,13-tetraazacyclohexadecane) was prepared by the reaction of trans-[Ru(16-TMC)Cl2]Cl with KCN in the presence of zinc powder. The oxidation of 1 with bromine gave trans-[Ru(16-TMC)(CN)2]+ isolated as PF6 salt (2.PF6). The Ru-C/C-N distances are 2.061(4)/1.130(5) and 2.069(5)/1.140(7) A for 1 and 2, respectively. Both complexes show a Ru(III/II) couple at 0.10 V versus FeCp2+/0. The UV-vis absorption spectrum of 1 is dominated by an intense high-energy absorption at lambda(max) = 230 nm, which is mainly originated from dpi(RuII) --> pi*(N[triple bond]C-Ru-C[triple bond]N) charge-transfer transition. Complex 2 shows intense absorption bands at lambda(max) <or= 228 nm and weaker vibronically structured absorption bands with peak maxima at 315-441 nm (epsilon(max) approximately (5-8) x 10(2) dm3 mol-1 cm-1), which are assigned to dpi(RuIII) --> pi*(N[triple bond]C-Ru-C[triple bond]N) and sigma(-CN) --> d(RuIII) charge-transfer transition, respectively. Density functional theory and time-dependent density-functional theory calculations have been performed on trans-[(NH3)4Ru(C[triple bond]N)2] (1') and trans-[(NH3)4Ru(C[triple bond]N)2]+ (2') to examine the Ru-cyanide interaction and the nature of associated electronic transition(s). The 230 nm band of 1 has been probed by resonance Raman spectroscopy. Simulations of the absorption band and the resonance Raman intensities show that the nominal nuC[triple bond]N stretch mode accounts for ca. 66% of the total vibrational reorganization energy. A change of nominal bond order for the cyanide ligand from 3 to 2.5 is estimated upon the electronic excitation.
Department of Chemistry and HKU-CAS Joint Laboratory on New Materials, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China.
Chun-Yuen
CY
Wong
Fu-Wa
FW
Lee
Chi-Ming
CM
Che
Yung Fong
YF
Cheng
David Lee
DL
Phillips
Nianyong
N
Zhu
D000588:Amines / Q000138:chemical synthesis / Q000737:chemistry*; D018360:Crystallography, X-Ray; D003486:Cyanides / Q000138:chemical synthesis / Q000737:chemistry*; D004563:Electrochemistry; D008024:Ligands; D047028:Macrocyclic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013059:Spectrum Analysis, Raman
D000588:Amines; D003486:Cyanides; D008024:Ligands; D047028:Macrocyclic Compounds; D009942:Organometallic Compounds; D012428:Ruthenium