For the first time, phosphorescence has been observed from and clearly assigned to the molecular triplet of several metallophthalocyanine (Pc) molecules. The Pc's of Pt, Pd, Cu, Zn, and Cd have O–O bands in solution (77°K) at the extraordinarily low energies of 10 590, 10 100, 9390, 9150, and 9120 cm−1, respectively, while those of Mg and VO have possible transitions at ∼9000 and 8500–8800 cm−1. Half-widths, lifetimes, approximate quantum efficiencies, triplet absorption, and excitation spectra, and vibrational substructure are reported, together with oxygenation and heavy atom effects. The lifetimes were very short (varying from 1 msec to less than 3 μsec), so room temperature phosphorescence was seen, as was radiation from the separate triplet sublevels at 4°K and below. Yields were very low (∼10−2 to ∼10−5) because of very strong radiationless transitions, and various other Pc complexes did not seem to phosphoresce at all. Both tripdoublet and quartet luminescence were seen from CuPc, and the intersystem crossing time was estimated to be ∼1 nsec. Fluorescence is reported from several of the complexes, including PdPc.

Free base Mg, ClAl, Zn, and Cu phthalocyanines (Pc’s) are successfully incorporated in Shpol’skii matrices, although they are practically insoluble in the open chain normal alkanes which are the conventional Shpol’skii solvents. In analogy with the porphyrins (P’s) the doublet spectra of the 0–0 transitions are observed. They are attributed to removal of the degeneracy of the first excited states in metal Pc’s, and to the existence of two tautomeric states in H2Pc. Relaxation between the doublet components, separated by several tens of cm−1, are slow at the experimental temperature, 4.2 K. Their relative fluorescence intensity is found for the first time to vary with the excitation wavelength. This is attributed to a strong vibronic mixing between the doublet components. The high resolution fluorescence-excitation and fluorescence spectra of the four investigated Pc’s incorporated in the Shpol’skii matrices are structurally very rich. They are characterized by weak electron–phonon and weak vibronic interactions in total accord with our previous findings with PtPc. While the electronic transition a1u(π)→eg(π*), accounts for most of the observed intensity, the numerous vibronic transitions, through weak, are laden with information. Qualitative analysis of the vibronic spectra helps to unravel the mechanism of vibronic coupling as well as to assign the vibronic bands unique to H2Pc and ClAlPc. There is strong indication from the electronic spectrum that the corresponding electronic state in ClAlPc is strongly perturbed by the presence of Cl. It is also found that the vibronic bands in the fluorescence-excitation spectra deviate markedly from their images in the fluorescence spectra in three aspects: relative intensity; extra vibronic activity; and band halfwidth. The causes of these differences are discussed.

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The luminescence properties of phthalocyanine complexes of platinum metals with d6 and d8 electron configurations were investigated in dilute solutions between room temperature and 1.6°K. For the first time it was possible to study the magnetic sublevels of the triplet state of aromatic molecules in zero field through optical detection methods alone. It was found that the lowest triplet state of these molecules has three zero field components of unequal splitting which depends on the central metal ion and which ranges from approximately 0.1–-10 cm−-1. Intersystem crossing populates solely the highest triplet component which does not radiate to the ground state, but which, in turn, populates the lower lying triplet components. The spin-lattice relaxation rates of these processes could be estimated to be of the order of 105 sec−1 at liquid helium temperature, and the triplet to ground state (S0← T1) decay rates were obtained. A noticeable solvent dependence of the radiationless rates was observed. The effect of spin-orbit coupling and radiationless energy transfer as a function of the metal ion in the phthalocyanine complexes is discussed. Surprisingly, Pd and Rh phthalocyanine were found to fluoresce as well as phosphoresce from essentially ligand-centered,excited states, an unusual occurrence in open d shell transition metal complexes.