Synthesis, Structural Characterization, Photophysical, Electrochemical, and Anion-Sensing Studies of Luminescent Homo- and Heteroleptic Ruthenium(II) and Osmium(II) Complexes Based on Terpyridyl-imidazole Ligand

Abstract

A series of hetero- and homoleptic tridentate ruthenium(II) and osmium(II) complexes of compositions [(tpy-PhCH(3))Ru(tpy-HImzphen)](ClO(4))(2) (1), [(H(2)pbbzim)Ru(tpy-HImzphen)](ClO(4))(2) (2), and [M(tpy-HImzphen)(2)](ClO(4))(2) [M = Ru(II) (3) and Os(II) (4)], where tpy-PhCH(3) = 4'-(4-methylphenyl)-2,2':6',2"-terpyridine, H(2)pbbzim = 2,6-bis(benzimidazole-2-yl)pyridine and tpy-HImzphen = 2-(4-[2,2':6',2"]terpyridine-4'-yl-phenyl)-1H-phenanthro[9,10-d]imidazole, have been synthesized and characterized by using standard analytical and spectroscopic techniques. X-ray crystal structures of three complexes 2, 3, and 4 have been determined. The absorption spectra, redox behavior, and luminescence properties of the complexes have been thoroughly investigated. All of the complexes display moderately strong luminescence at room temperature with lifetimes in the range of 10-55 ns. The effect of solvents on the absorption and emission spectral behavior of the complexes has also been studied in detail. The anion sensing properties of all the complexes have been studied in solution using absorption, emission, and (1)H NMR spectral studies and by cyclic voltammetric (CV) measurements. It has been observed that the complexes 1, 3, and 4 act as sensors for F(-)only, whereas 2 acts as sensor for F(-), AcO(-), and to some extent for H(2)PO(4)(-). It is evident that in the presence of excess of anions deprotonation of the imidazole N-H fragment(s) occurs in all cases, an event which is signaled by the development of vivid colors visible with the naked eye. The receptor-anion binding/equilibrium constants have been evaluated.

Light Harvesting and Directional Energy Transfer in Long‐Lived Homo‐ and Heterotrimetallic Complexes of FeII, RuII, and OsII

“…[27,28,39,40] The MLCT transitions are typically observed for each chromophoric metal center and each coordinated polypyridine acceptor ligand. Thus, in both Fe II -containing complexes (3 and 6), an intense band at 575 nm was observed, which is readily assigned to an Fe II !tpy (of tpy-Hbzim-phen) MLCT transition.…”

“…(dp) 5 bpy/phen-Hbzim-tpy(p*) 1 ] MLCT transitions that directly populate the triplet MLCT state. [27,28,40] In the UV region, very intense absorptions due to overlapping bipy-and phen-Hbzim-tpy-based n!p* and p!p* transitions are observed. It is evident that the absorption spectra of the homo-and heterotrimetallic complexes are an approximate superposition of those of the mononuclear model compounds.…”

A novel colorimetric and fluorescent sensor for fluoride detection based on a three-arm phenanthroline derivative

“…The anion examined including F -, CH 3 COO -, H 2 PO 4 -, Cl -, Br -, I -, HSO 4 -, and NO 3 -. The results obviously showed that the fluorescence intensity (at 443 nm) of trisphen markedly decreased upon the addition of 5 9 10 -4 M F -and CH 3 COO -, which may be ascribed to strong hydrogen bonding interaction between imidazole ring of receptor trisphen and anion [30,31], whereas all the other anions examined had a little change on that of receptor trisphen. Figures 6 and Figure S2 displayed the evolution of emission spectra of receptor trisphen with F -and CH 3 COO -in different concentrations, respectively.…”

(4′-Phenyl-2,2′:6′,2′′-terpyridine-κ3N,N′,N′′)bis(thiocyanato-κN)zinc(II) unknown solvate

“…Polydentate ligands containing N-donor heterocyclic rings are versatile building blocks in the construction of coordination compounds because of their ability to form stable complexes with transition metals and their various coordination modes (Hancock, 2013;Li et al, 2011;Bhaumik et al, 2011). One such ligand is 4 0 -phenyl-2,2 0 :6 0 ,2 00 -terpyridine (pypyt), first synthesized by Constable et al (1990) and used by them for the formation of nickel complexes.…”