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Cyclometalated Platinum(II) Terpyridylacetylide with a Bis(arylamine) Donor as a Proton-Triggered Luminescence Chemosensor for Zn2+

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journal contribution
posted on 17.08.2015, 00:00 by Dongfang Qiu, Mengmeng Li, Qian Zhao, Hongwei Wang, Chunxia Yang
A cyclometalated Pt­(II) acetylide derivative bearing a bis­(arylamine) donor (D) and a terpyridine (TPY) receptor (A) was successfully synthesized and characterized. This three-component D−π–A system displays an intense low-energy absorption band at λmax = 470 nm, resulting from overlapping the dπ­(Pt) → π*­(C^N^N) metal-to-ligand charge transfer and π­(CC–Ar) → π*­(C^N^N) ligand-to-ligand charge transfer transitions with the π­(bis­(arylamine)) → π*­(C^N^N) intraligand charge transfer transition. Upon protonation of the bis­(arylamine) donor, a strong emission from the phosphorescence Pt­(II) complex unit is recovered at λmax = 580 nm. With introduction of the TPY receptor, this complex possesses quite high affinity for Zn2+ (Ka = 6.86 × 109 mol–2·dm6) to form the heterotrinuclear Pt–Zn–Pt complex in CH2Cl2 solution. Though this coordination effect is seriously inhibited by protons in acidic medium, the 2.4-fold luminescence intensity enhancement is obtained yet, strongly suggesting the presence of the intramolecular energy transfer process from the Zn­(II)-TPY complex core to the phosphorescence Pt­(II) complex units at two ends. The H+-triggered and Zn2+-enhanced luminescence can be reversibly switched on and off upon successive additions of H+ and OH. Furthermore, this complex displays an unexpected Zn2+-selective luminescence enhancement effect in acidic solution.