Comparative spectroscopic and electrochemical properties of bis(octakis(dodecylthio)naphthalocyaninato)europium(III) and bis(tetra-tert-butylnaphthalocyaninato)europium(III) complexes

Bis(substituted-2,3-naphthalocyaninato)europium(III) complexes: bis(octakis (dodecylthio)-2,3-naphthalocyaninato)europium(III) {Eu[2,3-Nc(SC12H25)(8)]( 2), 1} and bis(tetra-tert-butyl-2,3-naphthalocyaninato)europium(III) {Eu-[2 ,3-Nc(t-Bu)(4)](2), 2} have been synthesized by cyclic tetramerization of n aphthalonitriles with Eu(acac)(3). H2O in the presence of 1,8-diazabicyclo[ 5.4.0]undec-7-ene (DBU) in refluxing n-octanol. These compounds were charac terized by UV-visible, magnetic circular dichroism (MCD), near-IR, IR, EPR, and mass spectroscopies. The absorption and MCD spectra of 1 showed splitt ing of the Q band, with peaks at 700 and 784 nm, red shifted from the Q ban d of 2 at 763 nm. The absorption and MCD spectral band deconvolution calcul ations of complex 1 gave two A terms in the Q-band region. The A terms are assigned to (2)A(2) --> E-2(1) transitions. Cyclic voltammograms of 1 and 2 showed reversible oxidation couples at E-1/2 = -0.28 V (for 2) and -0.25 V (for 1) vs ferrocenium/ferrocene (Fc(+)/Fc). The second oxidation exhibite d a complicated behavior for both complexes. The reduction couples for 2 we re observed at E-1/2 = -0.61, -1.64, -1.97, and -2.42 V, and for 1 they wer e observed at E-1/2 = -0.62, -1.60, -1.86, and -2.27 V vs Fc(+)/Fc. Spectra l changes observed on chemical oxidation and reduction of the complexes are presented, and the behaviors of 1 and 2 are compared.