Photo- and Electroluminescent Neutral Iridium(III) Complexes Bearing Imidoylamidinate Ligands

Imidoylamidinate-based heteroleptic bis(2-phenylbenzothiazole)iridium(III) and -rhodium(III) complexes [(bt)₂M(N^∩N)] (bt = 2-phenylbenzothiazole, N^∩N = N'-(benzo[d]thiazol-2-yl)acetimidamidyl (Ir1 and Rh1), N'-(6-fluorobenzo[d]thiazol-2-yl)acetimidamidyl (Ir2), N'-(benzo[d]oxazol-2-yl)acetimidamidyl (Ir3), N'-(1-methyl-1H-benzo[d]imidazol-2-yl)acetimidamidyl (Ir4); yields 70-84%) were obtained by the reaction of the in situ-generated solvento-complex [(bt)₂M(NCMe)₂]NO₃ and benzo[d]thia/oxa/N-methylimidozol-2-amines in the presence of NaOMe. Complexes Ir1-4 exhibited intense orange photoluminescence, reaching 37% at room temperature quantum yields, being immobilized in a poly(methyl methacrylate) matrix. A photophysical study of these species in a CH₂Cl₂ solution, neat powder, and frozen (77 K) MeOC₂H₄OH-EtOH glass matrix─along with density-functional theory (DFT), ab initio methods, and spin-orbit coupling time-dependent DFT calculations─verified the effects of substitution in the imidoylamidinate ligands on the excited-state properties. Electrochemical (cyclic voltammetry and differential pulse voltammetry) and theoretical DFT studies demonstrated noninnocent behavior of the imidoylamidinate ligands in Ir1-4 and Rh1 complexes due to the significant contribution coming from these ligands in the HOMO of the complexes. The iridium(III) species exhibit a ligand (L, 2-phenylbenzothiazole)-centered (³LC), metal-to-ligand (L', imidoylamidinate) charge-transfer (³ML'CT,³MLCT) character of their emission. The imidoylamidinate-based iridium(III) species were proved to be effective as the emissive dopant in an organic light-emitting diode device, fabricated in the framework of this study.

1,2-Dihydro-1,3,2-diazaborinine tautomer as an electron-pair donor in hydrogen-bonded complexes

Ab initio MP2/aug’-cc-pVTZ calculations have been carried out to investigate 1,2-dihydro-1,3,2-diazaborinine:HX complexes for HX = H+, HF, HCl, H2O, HCN, NH3, HCP, and HCCH. Most complexes are stabilized by linear, traditional hydrogen bonds except for those with H2O and NH3, which have bridging structures and nonlinear hydrogen bonds. H-atom transfer from N to B can occur in complexes with HF and HCl, with formation of a traditional F–H···N bond and a proton-shared Cl···H···N bond. The binding energies of the uncharged complexes range from 25 to 88 kJ mol−1. Spin-spin coupling constants have been used to characterize these hydrogen-bonded complexes.

Ferromagnetically coupled dinuclear MII complexes based on a boratriazine ligand framework

A boratriazine ligand, which incorporates attractive features from both bodipy and terpy, has been used to synthesize [Fe2II(μ1,1-N3)2(Py2F2BTA)2(N3)2] (1) and [Co2II(μ1,1-N3)2(Py2F2BTA)2(N3)2] (2). Both 1 and 2 feature a double end-on azido bridging motif, which promotes ferromagnetic interactions between the metal centres. Indeed, 1 represents the first report of a dinuclear FeII complex with this bridging mode exhibiting J = 5.7(9) cm-1 and D = -6.0(4) cm-1, while the isostructural Co analogue shows J = 7.1(9) cm-1 and D = 17.3(9) cm-1.