2,2′:6′,2″-Terpyridine meets 2,6-bis(1H-1,2,3-triazol-4-yl)pyridine: tuning the electro-optical properties of ruthenium(ii) complexes

Abstract

The synthesis of a series of heteroleptic ruthenium(ii)-complexes containing both, 2,2':6',2''-terpyridine and 2,6-bis(1H-1,2,3-triazol-4-yl)pyridine, is reported for the first time. The provided complexes feature photophysical and electrochemical properties in between those known for the respective homoleptic complexes. The flexibility with respect to lateral functional groups to be introduced into the complexes underlines the high potential for further functionalization steps.

The btp [2,6-bis(1,2,3-triazol-4-yl)pyridine] binding motif: a new versatile terdentate ligand for supramolecular and coordination chemistry

“…discussion above). 98,100 The photophysical properties of the heteroleptic complexes were found to be between those of the reference homoleptic complexes. Complex [Ru(39a)(terpy)](PF 6 ) 2 displayed an intense MLCT band at a wavelength (432 nm) exactly half way between the MLCT bands shown by the two homoleptic complexes, while the LC band was split in a distinctive fashion with two maxima corresponding to the peaks observed for the individual homoleptic complexes, indicating that the two ligands were electronically different in the Ru(II) coordination sphere.…”

“…Solvent choice has relatively little effect on yields, and it appears to be a matter of preference and, sometimes, solubility of starting materials that determines the choice of solvent systems. Alcohols like ethanol 87,95,97,98 and tert-butyl alcohol 93,94,96 mixed with water are most common in the literature, while DMSO (with 99 or without 100 water), THF, 60 CH 3 CN 101 and DMF 70,91 are also attested.…”

“…59,60,93,95,97,98,100,105,106,111,128,129 Flood and co-workers showed that Ru(II) forms stable coordination compounds with 3b. X-ray crystal crystallography showed a 1 : 2 metal : ligand stoichiometry, with the ligands adopting a distorted octahedral geometry, as demonstrated in Fig.…”

“…In recent years, Schubert and various co-workers have published prolifically in the field of Ru(II) coordination by btp-containing ligands, mostly with regard to the preparation of heteroleptic Ru(II)-complexes of terpy and btp ligands, 97,98,100 and Ru(II) complexes containing p-conjugated ditopic btp ligands. 95 Single crystals suitable for X-ray diffraction studies were obtained of [Ru(40a)(4-Br-f-terpy)](PF 6 ) 2 , with the structure shown in Fig.…”

“…The blue-shift in the MLCT as terpy ligands were replaced with btp was attributed to more efficient back-bonding, raising the LUMO energy, as well as lowering of the HOMO with increasing p-acceptor character of the ligands. 98 It was also noted that whereas addition of the electron-withdrawing 4-bromophenyl group in the central 4-pyridyl position of terpy led to significant red-shift of the MLCT band, the variation of substituents between ligands 39, 40 and 41 seemed to have negligible influence on the complexes' photophysical properties. This is in agreement with the insensitivity of electrochemical properties to 'arm' substituents described above.…”