The important role of coordination geometry on photophysical properties of blue-green emitting Ruthenium(II) diisocyano complexes bearing 2-benzoxazol-2-ylphenolate

Pui Yu HO, Shun-Cheung CHENG, Shek-Man YIU, Ka Man Vonika AU, Jing XIANG, Chi Fai LEUNG, Chi-Chiu KO

Research output: Contribution to journalArticle

Abstract

A series of blue-green emitting RuII diisocyano complexes containing 2-benzoxazol-2-ylphenolate (PBO) have been prepared. The complexes were isolated under varied reaction conditions in two isomeric forms, i.e., trans,trans,trans- (1) and cis,trans,cis- (2), with varied ligand coordination geometry above the RuII center. The photoluminescence of the isomeric complexes has been compared and tuned by the systematic variation of the electronic properties of the isocyanides. The cis,trans,cis- isomers exhibit structureless emission in the blue-green region (471–517 nm) upon excitation at λex > 400 nm in dichloromethane solution at room temperature. Both isomeric forms show similarly structured greenish emission at 499–523 nm on excitation at λex > 355 nm in a methanol/ethanol (4:1) glassy medium at 77 K. On careful comparison with the corresponding absorption and electrochemical data, it is suggested that the solution emission of the cis,trans,cis- isomers (2) at room temperature is originated from the metal-to-ligand charge transfer (MLCT), while a ligand-centered (LC) parentage is assigned for the emission in a glassy state for both isomeric forms. In line with the above experimental results, DFT calculation demonstrates the change in the nature and relative energy of the HOMOs and LUMOs with respect to the varied ligand coordination geometry and π-accepting ability of the isocyanides. Copyright © 2019 American Chemical Society.
Original languageEnglish
Pages (from-to)11372-11381
JournalInorganic Chemistry
Volume58
Issue number17
Early online dateAug 2019
DOIs
Publication statusPublished - 2019

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Bearings (structural)
Ruthenium
ruthenium
Ligands
ligands
Geometry
Cyanides
geometry
Isomers
isomers
Methylene Chloride
room temperature
Discrete Fourier transforms
Electronic properties
excitation
Methanol
Charge transfer
Photoluminescence
ethyl alcohol
Ethanol

Citation

Ho, P.-Y., Cheng, S.-C., Yiu, S.-M., Au, V. K.-M., Xiang, J., Leung, C.-F., & Ko, C.-C. (2019). The important role of coordination geometry on photophysical properties of blue-green emitting Ruthenium(II) diisocyano complexes bearing 2-benzoxazol-2-ylphenolate. Inorganic Chemistry, 58(17), 11372-11381. doi: 10.1021/acs.inorgchem.9b00560