Simultaneous observation of low temperature 4f-4f and 3d-3d emission spectra in a series of Cr(III)(ox)Ln(III) assembly

We report here the low temperature emission spectra in the heterometal dinuclear 3d-4f assembled molecular system [(acaC)(2)Cr-III(mu-ox)Ln(III)(HBpz(3))(2)] (Cr(ox)Ln:acac(-) = acetylacetonate, ox(2-) = oxalate, HBpz(3)(-) = hydrotris(pyrazol-1-yl)-borate; Ln = La, Nd, Ho, Er, Tm and Yb) in comparison with those of Na[Cr(acac)(2)(ox)] and [(HBpz(3))(2)Ln(mu-ox)Ln(HBpz(3))(2)](Ln = Nd and Er). From 10 to 150 K the Cr(ox)Ln complexes show a broad emission band around 800 nm from the E-2 state of Cr(III) moiety. At room temperature no E-2-(4)A(2) emission was observed in the Cr(ox)Ln except for the La and Lu complexes. On warming from 10 to 300 K rapid quenching of the E-2-(4)A(2) emission of Cr(III) is suggested to result from the energy transfer from Cr to Ln in the Cr(ox)Ln. The excitation spectra and the life-time were also measured with monitoring the 4f-4f emission peaks of the Cr(ox)Yb complex. (C) 2002 Elsevier Science B.V. All rights reserved.