Spectroscopy, photophysical properties, and X-ray crystal structure of platinum(II) complexes of quaterpyridine

Abstract

Two novel platinum quaterpyridine complexes have been synthesized and characterized by 1H NMR spectroscopy and X-ray crystallography: [Pt(pQP)](ClO4)2 (pQP = 3″,5,5′,5‴-tetramethyl-2,2′:6′,2″:6″, 2‴-quaterpyridine), monoclinic C2/c, a = 14.276 (2) Å, b = 12.970 (2) Å, c = 14.257 (1) Å, β = 102.29 (1)°, V = 2579.2 (6) Å3, Z = 4; [Pt(QP)](ClO4)2 (QP = 2,2′:6′,2″:6″,2‴-quaterpyridine), monoclinic P21, a = 5.904 (3) Å, b = 12.943 (2) Å, c = 14.300 (4) Å, β = 100.70 (4)°, V = 1073.7 (6) Å3, Z = 2. The shortest intermolecular Pt-Pt distances in [Pt(pQP)](ClO4)2 and [Pt(QP)](ClO4)2 are 7.249 (2) and 5.904 Å, respectively. Both complexes exhibit photoluminescence in the solid state at 700 nm. Only [Pt(pQP)]2+ shows room-temperature emission in acetonitrile (φf = 0.026 ± 0.001, lifetime at infinite dilution = 7.0 ± 0.6 μs, self-quenching rate constant = 2.9 ± 0.4 × 108 M-1 s-1). The excited state of [Pt(pQP)]2+ is a powerful oxidant with an E° value of about 2.3 V vs NHE. © 1992 American Chemical Society.