15min:

AI SAKAMOTO, MASATO HAYASHI, KENSUKE HARADA, KEIICHI TANAKA AND TAKEHIKO TANAKA, Department of Chemistry, Faculty of Sciences, Kyushu University, Hakozaki, Higashiku, Fukuoka, 812-8581 JAPAN.

Infrared spectrum of CoNO has been measured in low temperature Ar matrix and the ₁ and ₃ band origins were reported to be 1761.0 and 620.1 cm^-1 respectively. Recent DFT calculations suggested that the linear form (X¹ ) and bent form (X³A') of CoNO have almost the same energies.^a In the present study, the pure rotational spectrum of CoNO generated in a supersonic jet expansion by ultraviolet photolysis of Co(CO)₃NO was observed in the millimeter-wave region. This is the first observation of the rotationally resolved spectrum of the transition metal nitrosyl in the gas phase. Seven rotational transitions (from J =6-5 to 12-11) were measured in the frequency region of 56-112 GHz. Each rotational transition was split into 8-11 components due to hyperfine interaction of the Co (I=7/2) nucleus. The spectrum was analyzed to determine molecular constants, including the rotational constant B , centrifugal distortion constant D , nuclear quadrupole interaction constant eQq , and nuclear spin-rotation interaction constant C_I . From the observed spectral pattern, it is confirmed that CoNO has a linear structure and the electronic ground state is ¹ . The Co-N bond length was calculated to be 1.588 Å ~from the rotational constant, which is by 0.1 Å ~shorter than the Co-C bond length of CoCO. Measurement of rotational transitions in the ₂ vibrationally excited state is in progress.