Luminescent platinum(II) complexes. Electronic spectroscopy of platinum(II) complexes of 2,2′:6′,2″-terpyridine (terpy) and p-substituted phenylterpyridines and crystal structure of [Pt(terpy)CI][CF3SO3]

Abstract

The complexes [Pt(terpy)L′]ⁿ⁺(terpy = 2,2′:6′,2″-terpyridine; L′= Cl, Br, I, N₃ or SCN^–, n= 1; L′= NH₃, n= 2) have been prepared and their spectroscopic and emission properties studied. Absorption bands are found at 300–350 and at 370–450 nm, which are assigned to the intraligand and metal-to-ligand change-transfer (m.l.c.t.) transitions, respectively. The complexes [Pt(4′R-terpy)Cl]ClO₄(R′= C₆H₄OMe-p,C₆H₄Me-p, C₆H₄Br-p or C₆H₄CN-p) were prepared by the reaction of K₂[PtCl₄] with 4′R-terpy in water–MeCN. Unlike [Pt(terpy)L′]ⁿ⁺ which show emission in the solid state only, [Pt(4′R-terpy)Cl]⁺ display ³m.l.c.t. emission in fluid solution at room temperature. The crystal structure of [Pt(terpy)Cl][CF₃SO₃] has been determined: monoclinic, space group P2₁/n, a= 13.808(4), b= 6.873(1), c= 19.477(5)Å, β= 105.54(2)°, and Z= 4. In the unit cell, two [Pt(terpy)Cl]⁺ cations stack in a head-to-tail fashion with an intermolecular Pt ⋯ Pt distance of 3.329(1)Å. The solid-state emission of [Pt(terpy)Cl][CF₃SO₃] is similar to that of the ³(d_σ*π^b) emission of the dinuclear complex [Pt₂(terpy)₂L][ClO₄]₃(L = guadinate) having intramolecular Pt ⋯ Pt separations of 3.090(1) and 3.071(1)Å.