Infrared
photodissociation spectroscopy of Co+(NH3)n and Ni+(NH3)n: preference for tetrahedral or square-planar coordination
Toshitaka Imamura,a Kazuhiko Ohashi,*b Jun Sasaki,a Kazuya Inoue,a Kazuki Furukawa,a Ken Judai,c Nobuyuki Nishic and Hiroshi Sekiyab
Supplementary Information
IR spectra of Co+(NH3)n (n = 4–8) without N2 tagging Fig. S1 displays the IR photodissociation spectra of Co+(NH3)n with n = 4–8. Since the D4
value is larger than the IR photon energy, we preferentially detect a warm subset of the n = 4 ions that have internal energies sufficient to assist the elimination of an NH3 molecule following the IR absorption. As a result, the absorption features of Co+(NH3)4 (Fig. S1a) are
considerably broader than those of Co+(NH3)4·N2 (Fig. 2i).
Co+(NH3)6. The coordination structure of the n = 6 ion is particularly interesting, because Co+Ar6 was found to be anomalously stable,24 and an octahedral coordination was proposed for this ion.22 The experimental IR spectrum of Co+(NH3)6 (Fig. S2a) has a general
resemblance to the n = 5 spectrum. The resemblance makes us suppose that the Co+(NH3)6 ions have 4-coordinated structures that contain Co5IA or Co5IB as a subunit. structures and IR spectra of such (4+2) isomers are given in Fig. S2b–d. The optimized
Co6IA has two
double acceptors in the second shell, whose spectrum is similar to that of Co5IA. Co6IB has two single acceptors, whose spectrum is similar to that of Co5IB. Co6IC has a double and a From our DFT
single acceptor, whose spectrum is a mixture of those of Co5IA and Co5IB.
calculations, the difference in the energies of these (4+2) structures falls within ≈1 kJ mol-1. The experimental spectrum can be reproduced by a superposition of the theoretical spectra of these (4+2) structures.
Supplementary Material (ESI) for PCCP This journal is © the Owner Societies 2010
It is worth examining isomers