Ab initio Molecular Orbital Study of Emission Mechanism of 2,6-Bis(quinolinecarboxy)methylpyridine as Fluorescent Chemosensors for Zinc and Cadmium Ions

Jun KAWAKAMIa*, Ryo MIYAMOTOa*, Kimiaki KIMURAa, Kazuhiro OBATAa, Masahiko NAGAKIa and Haruo KITAHARAb

aDepartment of Materials Science and Technology, Faculty of Science and Technology, Hirosaki University
Bunkyo-cho 3, Hirosaki, Aomori 036-8561, Japan
bDepartment of Natural Science, Faculty of Education, Hirosaki University
Bunkyo-cho 1, Hirosaki, Aomori 036-8560, Japan

(Received: March 3, 2003; Accepted for publication: June 9, 2003; Published on Web: June 30, 2003)

2,6-Bis(quinolinecarboxy)methylpyridine (P2Q) was synthesized as fluorescent chemosensors for metal ions. P2Q hardly shows fluorescence itself, but it showed strong fluorescence with the addition of zinc or cadmium ions (If,Zn > If,Cd). Therefore, the Ab initio molecular orbital calculations (Gaussian 98) using the time-dependent density functional method with 6-31+G(d) basis set were carried out for a quinoline chromophore of P2Q and its metal complexes to investigate the emission mechanisms. The results of the molecular orbital calculations suggest that the lowest luminescent state has changed from the np* to the pp* by coordinating with a metal ion.

Keywords: Ab initio molecular orbital calculation, Time-dependent DFT, Quinoline, Zinc, Cadmium, Metal ion recognition, Fluorescent chemosensor

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