Synthesis, structures and photophysical properties of four binuclear Cu(I) complexes of 1H-imidazo[4,5-f][1,10]phenanthroline

Photophysical properties of homobimetallic Cu(i)–Cu(i) and heterobimetallic Cu(i)–Ag(i) complexes of 2-(6-bromo-2-pyridyl)-1H-imidazo[4,5-f][1,10]phenanthroline

“…All the bond lengths are comparable to those of similar complexes previously reported. 19,29,30,[38][39][40][41][42][43][44]46,56,61,63,[67][68][69][70] As expected, in heterobinuclear Cu(I)-Ag(I) complexes, deprotonated imidazole rings tend to act as softer donors and bind with the softer Lewis acid, Ag(I) ions. It is obvious that the distances of Ag-N and Ag-P are longer than those of the corresponding Cu-N and Cu-P because of the larger radii of Ag(I) ions.…”

“…Such distortion is particularly evident when observed from the bond angles, with those for other related complexes. 19,29,30,[38][39][40][41][42][43][44]46,68 The N-Cu-N (79.06-81.251) and N-Ag-N (71.00-71.421) angles are much smaller than those of P-Cu-P (113.90-120.901), P-Ag-P (110.87-112.281), N-Cu-P (98.57-133.741) and N-Ag-P (93.96-139.571) due to the limited bite angles of bpipH and its deprotonated form. The bond lengths of Cu-N and Cu-P are in the range of 2.039(3)-2.213(3) Å and 2.208(2)-2.288(1) Å, respectively, while the Ag-N bond and Ag-P bond lengths are in the range of 2.264(3)-2.491(4) Å and 2.404(2)-2.524(2) Å, respectively.…”

“…Based on this consideration, 1H-imidazole [4,5-f] [1,10] phenanthroline (Imphen) and its derivatives (Imphens) have become frequently used a-diimine derivatives. 19,30,[38][39][40][41][42][43][44][45][46] Second, the introduction of substituents at the ortho positions of the a-diimine coordination sites is a good way to gain better emission, because it can increase the steric hindrance of the coordination sites and reduce the quenching of luminescence caused by the attack of solvent molecules, especially water molecules. 4,15,37,[47][48][49][50][51] For instance, a highly luminescent Cu(I) complex has been reported by introducing two methyl groups to the 6,6 0 -positions of 4,4 0dimethyl-2,2 0 -bipyridine (dmbpy).…”

“…37 Third, bulky diphosphine ligands with strong chelating ability and good rigidity such as 9,9-dimethyl-4,5-bis(diphenylphosphino)-9H-xanthene (xantphos) and bis[(2-diphenylphosphino)phenyl] ether (POP) are often adopted. [38][39][40][41][42][43][44] The strong binding ability of such soft Lewis bases can effectively prevent the dissociation of the Cu(I) complexes in the solutions. The bulkiness and good rigidity can significantly reduce the structural distortion of the Cu(I) complexes and therefore enhance their emission yields.…”

“…As discussed earlier, among the reported a-diimine-Cu(I)-phosphine heteroleptic systems, Imphens have become much favored a-diimine derivatives in recent years because of their large conjugation degree, multiple coordination sites and good light-harvesting ability. 19,29,30,[38][39][40][41][42][43][44]48,68 Deprotonated Imphens are expected to serve as good bridging ligands for the synthesis of heteronuclear Cu(I)-Ag(I) complexes because the anionic imidazole rings will act as more soft donors.…”