Synthesis and characterization of tris(heteroleptic) diimine complexes of chromium(III)

Beyond Chiral Organic (p-Block) Chromophores for Circularly Polarized Luminescence: The Success of d-Block and f-Block Chiral Complexes

“…While the two former ions are known to be non-emissive, Cr III complexes are known to show NIR emission in the 600–800 nm region, arising from the two low-lying Cr III ( 2 E) and Cr III ( 2 T 1 ) spin–flip excited states ( Figure 13 ) (Jamieson et al, 1981 ; Kirk, 1981 , 1999 ; Forster, 1990 , 2002 ; Buldt and Wenger, 2017 ; Otto et al, 2018 ). In fact, Cr III complexes have long been known to exhibit interesting photophysical and photochemical properties as illustrated by the archetypal ter-bidentate [Cr(phen) 3 ] 3+ (Serpone et al, 1979 ; Ryu and Endicott, 1988 ; Isaacs et al, 2006 ; Donnay et al, 2007 ; Vandiver et al, 2010 ; Vasudevan et al, 2010 ; Doistau et al, 2018 , 2020 ), bis-terdentate [Cr(tpy) 2 ] 3+ (Serpone et al, 1979 ; Scarborough et al, 2012 ; Constable et al, 2014 ; Schönle et al, 2015a , b ; Barbour et al, 2017 ), and analogs (Zare et al, 2017b ; Jiménez et al, 2018 ). In all cases, the ligand-field strength induced by the phen and tpy ligands is strong enough to induce near-infrared phosphorescence arising from the lowest-lying Cr( 2 T 1 ) and Cr( 2 E) excited states, but the associated very low quantum yields (<0.2%) are strong limitations for their use as CPL probes.…”

“…have long been known to exhibit interesting photophysical and photochemical properties as illustrated by the archetypal terbidentate [Cr(phen) 3 ] 3+ (Serpone et al, 1979;Ryu and Endicott, 1988;Isaacs et al, 2006;Donnay et al, 2007;Vandiver et al, 2010;Vasudevan et al, 2010;Doistau et al, 2018Doistau et al, , 2020, bisterdentate [Cr(tpy) 2 ] 3+ (Serpone et al, 1979;Scarborough et al, 2012;Constable et al, 2014;Schönle et al, 2015a,b;Barbour et al, 2017), and analogs (Zare et al, 2017b;Jiménez et al, 2018). In all cases, the ligand-field strength induced by the phen and tpy ligands is strong enough to induce near-infrared phosphorescence arising from the lowest-lying Cr( 2 T 1 ) and Cr( 2 E) excited states, but the associated very low quantum yields (<0.2%) are strong limitations for their use as CPL probes.…”

Key Strategy for the Rational Incorporation of Long-Lived NIR Emissive Cr(III) Chromophores into Polymetallic Architectures

“…The much cheaper Cr III N6 chromophores, which display long near infra-red (NIR) emission lifetimes that can reach the millisecond range in solution at room temperature, might be better suited for collecting and redistributing light-excitation. [35][36][37][38][39][40][41] Despite those outstanding photophysical properties which led to the first implementation of linear up-conversion in a molecular chromium-containing compound, [42][43][44][45] Cr III N6 inert complexes have been rarely introduced into designed polymetallic architectures because of (i) their only partial robustness regarding cross-coupling reactions, (ii) the scarce synthetic methods available for the preparation of heteroleptic Cr III complexes 38,[46][47][48][49][50][51] and (iii) the lack of accessible simple quantitative characterisation method in solution since highresolution NMR spectroscopy is hampered by the long electronic relaxation time of the Cr( 4 A2) paramagnetic ground state. Nonetheless, important efforts were focused on the synthesis of multimetallic Cr III -containing complexes for implementing magnetic properties.…”

Heterolepticmer-[Cr(N∩N∩N)(CN)3] complexes: synthetic challenge, structural characterization and photophysical properties

“…Synthesis and characterization of the heteroleptic mer-[Cr(L) (CN) 3 ] (L = tpy, ddpd and dqp) complexes Modern strategies used for the preparation of heteroleptic Cr III complexes are indebted to Kane-Maguire and co-workers, who took advantage of the unusual lability of the Cr III -O(triflate) bond in Cr(CF 3 SO 3 ) n adducts for the controlled synthesis of tri-didentate complexes. 66,67 Its extension for connecting two different tridentate binding units around six-coordinate Cr III was first reported by Constable and co-workers [59][60][61] and required the preparation of the mer-[Cr(L)X 3 ] (X = Cl, Br) intermediates prior to react them with HCF 3 SO 3 to form labile mer-[Cr(L)(CF 3 SO 3 ) 3 ] and HX. Although this method was proved to be effective with five-membered tpy-type chelating ligands, [59][60][61] its application with more basic six-membered ddpd and dqp ligands resulted in partial decomplexation and isolation of the protonated [Hddpd] + and [Hdqp] + ligands.…”