Zeeman studies of the first excited states of palladium and metal free phthalocyanines in Shpol'skii matrix

Abstract

Phthalocyanines (Pcs) are planar molecules of relatively high symmetry and exhibit magneto-optic effects in many ways. We report the Zeeman effect of the first excited states of palladium (Pd-) and free-base (H-2-) Pcs in a 5 K Shpol'skii matrix by direct observation of their fluorescence position shifts. From the experimental data an apparent angular momentum integral, coupling the lowest two Jahn-Teller stabilized crystal field split first excited states, Lambda', was found to be 2.7+/-0.1 (h) over bar for PdPc. No conclusive Lambda' was deduced for H(2)Pc but its value can be estimated to be around the theoretical value of 3 (h) over bar. The experimental data of H(2)Pc revealed a complex structure in the fluorescence band examined, which complicated the analysis of Lambda' but helped unravel the biexponential decay problem of the structure. We infer one narrower band in the structure has the previously reported lifetime of tau 6.3 ns, and the other broader band being similar to 1.8 cm(-1) higher, has tau 3.7 ns. We believe this composite situation also exists for the other tautomeric structure since it also exhibited biexponential decay. (C) 1996 American Institute of Physics.