Synthesis, Crystal Structure, Photophysical Property And Metal Ion-Binding Behavior Of A Cyclometalated Platinum(Ii) Terpyridylacetylide With Efficient Pi-Conjugation Degree

A cyclometalated Pt(II) acetylide derivative bearing a carbazole donor and a terpyridine (TPY) receptor has been successfully synthesized and characterized. X-ray crystallography shows its monoclinic crystal system with the P2(1)/c space group and the three-component co-planarity molecular structure. This efficient pi-conjugation system displays an intense low-energy absorption band (epsilon = 1.51 x 10(4) dm(3) mol(-1) cm(-1)) at lambda(max) = 442 nm and a strong phosphorescence emission (Phi = 0.045) at lambda(max) = 596 nm in an air-saturated CH2Cl2 solution at room temperature, resulting from the d pi(Pt) -> pi*(C<^>N<^>N) metal-to-ligand charge transfer (MLCT) mixing with the pi(C C-Ar) ->/pi*(C<^>N<^>N) ligand-to- ligand charge transfer (LLCT) transition. With the introduction of the TPY receptor, this complex possesses ca. 1.6-fold luminescence-enhancing response for Zn2+ and Cd2+ but dramatic luminescence quenching response toward other common transition metal cations. Consecutive titrations exhibit that the added metal ions bond to its free TPY receptor with 1 : 2 stoichiometry to form the heterotrinuclear (Pt-M-Pt) complex. The Fe2+-quenched and Zn2+-enhanced luminescence behaviors with the maximum PET efficiency of 92.4% and 62.7%, respectively, strongly suggest the presence of the intra-molecular energy transfer between the [M(TPY)(2)](2)+ core and the terminal phosphorescent Pt(II) complex units.