Hydrothermal syntheses, structural, Raman, and luminescence studies of Cm[M(CN)2]3·3H2O and Pr[M(CN)2]3·3H2O (M=Ag, Au): 2. Hetero-bimetallic coordination polymers consisting of trans-plutonium and transition metal elements

We have prepared Cm[Au(CN)2]3·3H2O and Cm[Ag(CN)2]3·3H2O as a part of our continuing investigations into the chemistry of the 5f-elements’ dicyanometallates. Single crystals of Cm[Au(CN)2]3·3H2O were obtained from the reaction of CmCl3 and KAu(CN)2 under mild hydrothermal conditions. Due to similarities in size, the related praseodymium compounds were also synthesized and characterized for comparison with the actinide systems. The compounds crystallize in the hexagonal space group P63/mcm, where the curium and the transition metals interconnect through cyanide bridging. Crystallographic data (Mo Kα, λ=0.71073 Å): Cm[Au(CN)2]3·3H2O (1), a=6.6614(5) Å, c=18.3135(13) Å, V=703.77(9), Z=2; Pr[Au(CN)2]3·3H2O (3), a=6.6662(8) Å, c=18.497(3) Å, V=711.83(17), Z=2; Pr[Ag(CN)2]3·3H2O (4), a=6.7186(8) Å, c=18.678(2) Å, V=730.18(14), Z=2. The Cm3+ and/or Pr3+ ions are coordinated to six N-bound CN− groups resulting in a trigonal prismatic arrangement. Three oxygen atoms of coordinated water molecules tricap the trigonal prismatic arrangement providing a coordination number of nine for the f-elements. The curium ions in both compounds exhibit a strong red emission corresponding to the 6D7/2→8S7/2 transition. This transition is observed at 16,780 cm−1, with shoulders at 17,080 and 16,840 cm−1 for the Ag complex, while the emission is red shifted by ∼100 cm−1 in the corresponding gold complex. The Pr systems also provide well-resolved emissions upon f–f excitation.