Infrared spectra of phthalocyanine and naphthalocyanine in sandwich-type (na)phthalocyaninato and porphyrinato rare earth complexes - Part 4. The infrared characteristics of phthalocyanine in heteroleptic tris(phthalocyaninato) rare earth complexes

The infrared (IR) spectroscopic data for a series of heteroleptic tris(phthalocyaninato) rare earth complexes (Pc)M(OOPc)M(OOPc) (M = Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu, Y) and (Pc)Tm(OOPc)Tm(Pc) [H2Pc = unsubstituted phthalocyanine, H2OOPc = 2,3,9,10,16,17,24,25-octakis(octyloxy)phthalocyanine] have been collected with 2 cm(-1) resolution. The IR spectra for (Pc)M(OOPc)M(OOPc) are more complicated than those of bis(phthalocyaninato) rare earth analogues, revealing the relatively lower symmetry of these triple-decker compounds. For both types of heteroleptic tris(phthalocyaninato) rare earth compounds, the characteristic phthalocyanine dianion IR bands for both Pc2- and OOPc2- at ca. 1329 and 1380 cm(-1) attributed, respectively, to the pyrrole stretching and the symmetric C-H bendings of -CH3 groups in octyloxy side chains of OOPc rings together with contribution from the isoindole stretching vibrations are observed in these spectra. The frequencies of the vibration at 1312-1318, attributed to pyrrole stretchings, are dependent on the central rare earth size, shifting slightly to higher energy along with the decrease of rare earth radius across the series. The decreased sensitivity of the frequency of the vibration at 1463-1465 cm(-1) and rare earth metal size compared with that of the corresponding isoindole stretching band at 1439-1454 cm(-1) for bis(phthalocyaninato) rare earth counterparts indicates that the pi-pi interactions in these heteroleptic triple-deckers are weaker than those in the double-deckers. (C) 2003 Elsevier B.V. All rights reserved.