A novel europium (iii) nitridoborate eu-3[b3n6]: synthesis, crystal structure, magnetic properties, and Raman spectra

Abstract

A novel europium (III) nitridoborate, Eu-3[B3N6], was successfully synthesized by oxidation of Eu-3(II)[BN2](2) with Br-2 at 1073 K. The compound crystallizes in the trigonal space group R (3) over barc (No:167) with a=11.9370(4) angstrom, c=6.8073(4) angstrom, and Z=6. The crystal structure of Eu-3[B3N6] consists of isolated, planar cyclic [B3N6](9-) units which are charge-balanced by Eu3+ cations. The oxidation state of Eu was investigated by Mossbauer spectroscopy, electron spin resonance (ESR) spectroscopy, and quantum chemical calculations. The Eu-151 Mossbauer spectroscopic measurement at 77 K reveals that the main signal at delta=0.93(7) mm/s is originating from trivalent Europium. Eu-3[B3N6] showed no ESR signal in accordance with a non-magnetic (J=0) F-7(0) ground state of the 4f(6) configuration. Quantum chemical calculations find six electrons in the 4f subshell (4f(6)) of Eu indicating an oxidation state of +3. We present for the first time the vibrational spectra of a compound with cyclic trimer [B3N6](9-) moieties. The Raman spectrum of Eu-3[B3N6] is in good agreement with the predicted number of modes for the spectroscopically relevant cyclic [B3N6](9-) group with D-3h symmetry.