Heteroleptic mer-[Cr(N∩N∩N)(CN)3] complexes: synthetic challenge, structural characterization and photophysical properties Chong, Julien Besnard, Céline Carlos M. Cruz, Carlos M. Piguet, Claude Jiménez Gallego, Juan Ramón The substitution of three water molecules around trivalent chromium in CrBr3·6H2O with the tridentate 2,2’:6’,2’’-terpyridine (tpy), N,N’-dimethyl-N,N’-di(pyridine-2-yl)pyridine-2,6-diamine (ddpd) or 2,6-di (quinolin-8-yl)pyridine (dqp) ligands gives the heteroleptic mer-[Cr(L)Br3] complexes. Stepwise treatments with Ag(CF3SO3) and KCN under microwave irradiations provide mer-[Cr(L)(CN)3] in moderate yields. According to their X-ray crystal structures, the associated six-coordinate meridional [CrN3C3] chromophores increasingly deviate from a pseudo-octahedral arrangement according to L = ddpd ≈ dpq ≪ tpy; a trend in line with the replacement of six-membered with five-membered chelate rings around CrIII. Room-temperature ligand-centered UV-excitation at 18 170 cm−1 (λexc = 350 nm), followed by energy transfer and intersystem crossing eventually yield microsecond metal-centered Cr(2E → 4A2) phosphorescence in the red to near infrared domain 13 150–12 650 cm−1 (760 ≤ λem ≤ 790 nm). Decreasing the temperature to liquid nitrogen (77 K) extends the emission lifetimes to reach the millisecond regime with a record of 4.02 ms for mer-[Cr(dqp)(CN)3] in frozen acetonitrile. 2024-10-03T11:48:04Z 2024-10-03T11:48:04Z 2022-02-17 journal article Chong, J. et. al. Dalton Trans., 2022, 51, 4297. [https://doi.org/10.1039/D2DT00126H] https://hdl.handle.net/10481/95486 10.1039/D2DT00126H eng http://creativecommons.org/licenses/by-nc/4.0/ open access Atribución-NoComercial 4.0 Internacional Royal Society of Chemistry