Abstract
| - Three axially substituted complexes, 2,3-octa(3,5-di-tert-butylphenoxy)-2,3-naphthalocyaninato indium chloride(1a), 2,3-octa(3,5-di-tert-butylphenoxy)-2,3-naphthalocyaninato indium bromide (1b), and 2,3-octa(3,5-di-tert-butylphenoxy)-2,3-naphthalocyaninato indium iodide (1c) have been synthesized and their photophysicalproperties have been investigated. Optical power limiting of nanosecond (ns) and picosecond (ps) laser pulsesat 532 nm using these complexes has been demonstrated. All complexes display strong Q(0,0) absorptionand measurable emission in the near-infrared region and exhibit strong excited-state absorption in the rangeof 470−700 nm upon ns laser excitation. The different axial ligands show negligible effect on the linearabsorption, emission, and transient difference absorption spectra. However, the excited-state lifetime, tripletexcited-state quantum yield, and efficiency to generate singlet oxygen are affected significantly by the heavieraxial ligand. Brominated and iodinated complexes 1b and 1c show higher triplet excited-state quantum yield,while chlorinated complex 1a has longer excited-state lifetime and is more efficient in generating singletoxygen. The iodinated complex 1c displayed the best optical limiting due to the higher ratio of excited-stateabsorption cross section to ground state absorption cross section (σeff/σ0).
|