Visible Spectra of Argon Matrix Isolated Phthalocyanines: Pair Interactions

The 5000–8000‐A transmission spectra of H2PC and CuPC embedded in an argon matrix at 5°K at molar ratios of 4000:1 are very similar to their spectra in liquid solution. The predominant CuPC species in the matrix are isolated molecules, but a strong sideband in more concentrated mixtures (1000 Ar:1 CuPC) is attributed to interacting pairs. Coupling of transition dipoles was invoked to correlate the observed spectrum with several CuPC “dimer” configurations. Computer calculations based upon nonbonded atom–atom potentials were conducted to find the most probable relative orientations of two neighboring solute CuPC molecules. H2PC does not appear to show the effects of pairs even in extremely dilute solutions. A strong doublet which is very similar to that in liquid solution persists in the matrix.