Synthesis, structures, and emissive properties of platinum(II) complexes with a cyclometallating aryldiamine ligand

A new series of square planar Pt(II) complexes with the mer-coordinating tridentate ligand, pip(2)NCN(-) (pip(2)NCNH = 1,3-bis(piperdylmethyl)benzene), has been prepared: Pt(pip(2)NCN)Cl (2), Pt(pip(2)NCN)Br (3), Pt(pip(2)NCN)I (4), and Pt(pip(2)NCN)(CH(3)N=C(CH(3))(2))]CF(3)SO(3)] (5). The complexes have been fully characterized by (1)H NMR spectroscopy, elemental analysis, and UV-vis spectroscopy. The X-ray crystal structures of pip(2)NCNBr (1), 2, and 5 are reported. Compound 1: triclinic, P, a = 10.081(1) A, b = 10.153(2) A, c = 10.390(1) A, alpha = 66.05(1) degrees, beta = 79.07(1) degrees, gamma = 64.51(1) degrees, V = 877.1(2) A(3), Z = 2. Complex 2: triclinic, P, a = 9.897(2) A, b = 10.191(2) A, c = 19.174(4) A, alpha = 75.09(3) degrees, beta = 76.14(3) degrees, gamma = 71.00(3) degrees, V = 1741.2(6) A(3), Z = 4. Complex 5: triclinic, P, a = 10.709(2) A, b = 11.2321(10) A, c = 12.447(2) A, alpha = 110.509(8) degrees, beta = 112.417(10) degrees, gamma = 91.066(9) degrees, V = 1276.1(3) A(3), Z = 2. In 77 K 3:1 EtOH/MeOH glassy solution, these colorless complexes exhibit weak red-orange to red emissions originating from a lowest spin-forbidden ligand field excited state.