@misc{10481/93747,
year = {2024},
month = {7},
url = {https://hdl.handle.net/10481/93747},
abstract = {Complete or partial replacement of well-known five-membered chelating 2,2’-bipyridine (bipy) or 1,10-
phenanthroline (phen) ligands with analogous didentate 2,2’-biimidazole (H2biim) provides novel perspectives
for exploiting the latter pH-tuneable bridging unit for connecting inert trivalent chromium with
cationic partners. The most simple homoleptic complex [Cr(H2biim)3]3+ and its stepwise deprotonated
analogues are only poorly soluble in most solvents and their characterization is limited to some solidstate
structures, in which the pseudo-octahedral [CrN6] units are found to be intermolecularly connected
via peripheral N–H⋯X hydrogen bonds. Moreover, the associated high-energy stretching N–H vibrations
drastically quench the targeted near infrared (NIR) CrIII-based phosphorescence, which makes these
homoleptic building blocks incompatible with the design of molecular-based luminescent assemblies.
Restricting the number of bound 2,2’-biimidazole ligands to a single unit in the challenging heteroleptic
[Cr(phen)2(Hxbiim)](1+x)+ (x = 2–0) complexes overcomes the latter limitations and allows (i) the synthesis
and characterization of these [CrN6] chromophores in the solid state and in solution, (ii) the stepwise and
controlled deprotonation of the bound 2,2’-biimidazole ligand and (iii) the implementation of Cr-centered
phosphorescence with energies, lifetimes and quantum yields adapted for using the latter chromophores
as sensitizers in promising ‘complex-as-ligand’ strategies.},
organization = {Swiss National Science Foundation
is gratefully acknowledged (grant 200020_207313)},
publisher = {Royal Society of Chemistry},
title = {Taming 2,2’-biimidazole ligands in trivalent chromium complexes†},
doi = {10.1039/D4DT01608D},
author = {Chong, Julien and Benchohra, Amina and Besnard, Céline and Guénée, Laure and Rosspeintner, Arnulf and Cruz, Carlos M. and Jiménez Gallego, Juan Ramón and Piguet, Claude},
}