Ru(II) and Os(II) Complexes Based on Terpyridyl-Imidazole Ligand Rigidly Linked to Pyrene: Synthesis, Structure, Photophysics, Electrochemistry, and Anion-Sensing Studies

Abstract

We report in this work a new family of bis-tridentate ruthenium(II) and osmium(II) complexes bearing a terpyridyl ligand rigidly link to pyrenyl-benzimidazole moiety (tpy-HImzPy = 10-(4-[2,2':6',2''-terpyridine]terpyridin-4'-yl-phenyl)-9H-9,11-diaza-cyclopenta[e]pyrene) along with other tridentate ligands such as 4'-(2-naphthyl)-2,2':6',2″-terpyridine (tpy-NaPh) and 2,6-bis(benzimidazole-2-yl)pyridine (H2pbbzim). All the complexes are thoroughly characterized by their elemental analysis, ESI mass spectrometry, and (1)H NMR spectroscopy. The molecular structures of two complexes [Ru(tpy-HImzPy)2](ClO4)2 (3) and [(pbbzim)Ru(tpy-HImzPy)] (2a) in the solid state were determined by X-ray crystallography. The absorption, steady-state, and time-resolved luminescence and electrochemical properties of all the four compounds have been studied. On excitation at their MLCT bands, all four compounds exhibit moderately strong room-temperature luminescence with lifetimes ranging between 3.8 and 161.1 ns in aerated condition, whereas in the deaerated (N2 purged) condition, the lifetimes vary between 8.2 and 199.1 ns, depending upon the nature of the solvents. The presence of imidazole N-H protons in all the complexes motivates us to study anion sensing properties of the complexes in solution through different channels. Spectrophotometeric, fluorometric, (1)H NMR spectroscopic, and cyclic voltammetric studies of the complexes in presence of anions reveal that the complexes sense principally F(-), CN(-), and to a lesser extent for AcO(-). Multichannel anion sensing studies also indicate that anion-induced deprotonation of the imidazole N-H protons occur in all four compounds. The equilibrium constant of this deprotonation steps have been estimated from UV-vis absorption and emission titration data. Anion-induced modulation of lifetimes makes all the four complexes suitable for lifetime-based sensors for selective anions.

Heteroleptic Phenanthroline Complexes of Trinuclear Molybdenum Clusters with Luminescent Properties

“…As can be seen in Figure 7, the addition of anions, such as F -, OH -, and AcO -, to a solution of complex 1 in DMF Figure 7. [38][39][40][41][42][43] Hence, the complexes reported herein are, to the best of our knowledge, the first example of receptors comprised of imidazophenanthroline ligands complexed to molybdenum clusters, and in the future, they could be the basis of a series of probes for anionic species, properly tuned to meet the sensitivity and selectivity requirements of a given application. OH -, (b) 100 equiv.…”

Polypyridyl-imidazole based smart Ru(II) complex mimicking advanced Boolean and Fuzzy logic functions

“…[38][39][40][41]. A number of Ru(II) complexes derived from polypyridine ligands were previously designed as the sensors for selective anions as well as cations, [37,[42][43][44][45][46][47][48] although such complexes for the construction of sequential molecular logic gates are extremely few in the literature [49][50][51][52][53][54]. In the present complex, the remote terpyridine chelating site is suitably oriented to bind with the incoming cationic guests.…”

Group 8 Metallomacrocycles – Synthesis, Characterization, and Stability

“…tems [4,10,[13][14][15][16] and grids. [17] Incorporation of Ͻtpy-Os IItpyϾ into 2-and 3-D architectures is largely unexplored.…”