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摘要
A long but adventurous journal to the synthesis of tetradentate bis-cyclometalated C boolean AND C*N boolean AND N-coordinated platinum complexes is described, where C boolean AND C and N boolean AND N denote a five-membered chelation and C*N denotes a six-membered chelation. Initial ligand designs resulted in the selective cycloplatination to form a tridentate coordination complex. The structures of the tridentate coordination complexes were confirmed by the X-ray crystallographic studies. The selective formation of the tridentate coordination complexes was analyzed, which led us to an ultimate design of the ligand 15 and 16. Ligands 15 and 16 differ only in the N boolean AND N motif; a bipyridine-based N boolean AND N for 15 and a pyrazolylpyridine-based N boolean AND N for 16, respectively. In both cases, a forced consecutive double cycloplatination would be possible to form a C boolean AND C*N boolean AND N-coordinated platinum complex. As expected, the reaction of ligand 15 and 16 with K2PtCl4 in acetic acid at reflux produced 17 and 18, respectively. The coordination geometry was confirmed by the X-ray crystallography of the complex 17. The square planar geometry and dual intermolecular pi-pi and Pt-Pt interactions were revealed in the molecular packing. The photophysical properties of the complexes were studied. It was found that the complex 18 emitted intensely yellow phosphorescence at room temperature in deoxygenated solution, while complex 17 emitted red emission in a frozen glass matrix. Both compounds have the lifetime of the excited states in the scale of micro seconds. The DFT calculations were carried out to elucidate the frontier orbitals of the complexes, which are used in interpreting the electronic spectra of the complexes.
- 出版日期2013-3-22
