Heteroleptic mer-[Cr((NNN)-N-boolean AND-N-boolean AND)(CN)(3)] complexes: synthetic challenge, structural characterization and photophysical properties Chong, Julien Jiménez Gallego, Juan Ramón Financial support from the Swiss National Science Foundation is gratefully acknowledged (grant numbers: 200020_178758 and 206021_183324). Carlos M. Cruz thankfully acknowledge Prof. Dr Michal Juricek for his support and access to the UZH Service and Support for Science IT (S3IT) computing facilities. 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. 2022-03-21T08:04:39Z 2022-03-21T08:04:39Z 2022-02-17 journal article Dalton Trans., 2022,51, 4297-4309. DOI: [10.1039/d2dt00126h] http://hdl.handle.net/10481/73584 10.1039/d2dt00126h eng http://creativecommons.org/licenses/by-nc/3.0/es/ open access Atribución-NoComercial 3.0 España Royal Society of Chemistry