Tetrakis(pyridine)ruthenium Trans Complexes of Phenylcyanamide Ligands:  Crystallography, Electronic Absorption Spectroscopy, and Cyclic Voltammetry

Abstract

The complexes trans- [Ru(py) 4 L 2 ] where py ) pyridine and L ) (2-chlorophenyl)-, (2,3-dichlorophenyl)-, (2,4,5-trichlorophenyl)-, (2,3,4,5-tetrachlorophenyl)-and (pentachlorophenyl)cyanamide were synthesized and characterized by electronic and 1 H NMR spectroscopies. A crystal structure of trans-[Ru(py) 4 ((2-chlorophenyl)cyanamide) 2 ] showed the expected trans coordination of the phenylcyanamide ligands. Crystal structure data: space group C2/c, with a, b, and c ) 40.6441(3), 9.2003(1), and 22.6946(2) Å, respectively, ) 116.387(1)°, V ) 7602.2(1) Å 3 , and Z ) 8. The structure was refined by using 4943 independent reflections with I > 2σ(I) to a final R factor of 0.060. Spectroelectrochemistry was used to generate the electronic absorption spectra of the Ru(III) complexes trans-[Ru(py) 4 L 2 ] + . Ru(III)-cyanamide coupling elements derived from charge transfer spectral data of the trans-[Ru(py) 4 L 2 ] + complexes were significantly larger than those of the corresponding [Ru(NH 3 ) 5 L] 2+ complexes.

Electronic Energy Transduction from {Ru(py)4} Chromophores to Cr(III) Luminophores

“…For example, pyridinic ligands with a variety of substituents at the 4-position are employable toward tuning the electronic structure. − Equally versatile are their solvento complexes as precursors as a means to realize unsymmetrically trans disubstituted {Ru­(py) 4 }. − A stable trans configuration assists in overcoming the steric constraints typically encountered in cis -{Ru­(bpy) 2 }, especially when larger bridged systems or densely covered surfaces are at stake . Diverse molecular architectures were built around these building blocks, ,− and cyanide-bridged molecular wires stand as notable examples. , Such a cyanide-based motif enables strong electronic coupling between the metal centers without detrimental traps or low-energy states that impede any efficient energy or charge migration. − …”

Charge Transfer Properties of Benzo[b]thiophene Ferrocenyl Complexes

“…The energy values of the LMCT bands of A + – D + , together with those of the cationic (ferrocenyl)­indenes 4 – 8 and (2-ferrocenyl)­cyclopenta­[ l ]­phenanthrene ( 9 ) previously reported by us, correlate well with the oxidation potential difference Δ E between the aryl groups and the ferrocenium (Figure ), with the exception of the C1 + /C2 + mixture, which displays a particularly low Δ E value. In an electrochromic system, the smaller the Δ E gap between the oxidation potentials of the metal group and the organic moiety results, the lower the occurrence of the NIR transition. , This correlation can be interpreted by using the classical two-state electron transfer model (Hush theory) applied to LMCT and MLCT transitions …”

trans-Dichloridotetrapyrazineruthenium(II) dichloromethane disolvate

“…These distances are on the low side of the narrow range of bond lengths when this complex is used in supramolecular assemblies (Carlucci et al, 2002), indicating very little influence on bond distance upon further coordination of this metal-based building block. Ru-N distances in tetrakis(pyridine)RuL 2 , are 2.09 Å (L = 2-chlorophenylcyanamide) (Desjardins, et al, 1999), or 2.08 Å (L = one chloride and one benzonitrile) (Coe et al, 1995). H-bonds and intermolecular contacts form a network in the crystal.…”

“…The synthesis of the title complex and its use as a building block in coordination networks are described by Carlucci et al (2002) and Coe (2004). For related structures using pyridine and varying trans ligands, see: Coe et al (1995); Desjardins et al (1999). T = 100 K 0.10 Â 0.10 Â 0.08 mm…”