Enyo Tomonori, Nicolaides Athanassios, Tomioka Hideo
Chemistry Department for Materials, Faculty of Engineering, Mie University, Tsu, Mie 514-8507, Japan.
J Org Chem. 2002 Aug 9;67(16):5578-87. doi: 10.1021/jo025877q.
m-Phenylene-coupled carbenonitrenes [(3-nitrenophenyl)methylene (2-H), (3-nitrenophenyl)fluoromethylene (2-F), (3-nitrenophenyl)chloromethylene (2-Cl), (3-nitrenophenyl)bromomethylene (2-Br)] have been investigated computationally (with B3LYP, MCSCF, CASPT2, ROMP2, and QCISD(T) methods) and experimentally (with IR, UV, and ESR spectroscopy). For each species, five electronic states were considered. At the highest level of theory explored, the parent compound (2-H) has a quintet ground state, but its halogen derivatives (2-X, X = F, Cl, and Br) have triplet ground states. A linear relationship between the Q[bond]T energy gap of 2-X and the T-S gap of the corresponding phenylcarbenes 8-X is found, which can be helpful in rationalizing and predicting ground-state multiplicities in m-phenylene-linked carbenonitrenes and similar species. Precursors for the photochemical generation of 2-X (X = H, F, Cl, and Br) were synthesized and photolyzed in matrixes (Ar, triacetin) at low temperatures. IR (Ar, 13 K) and ESR (triacetin, 77 K) data are compatible with the generation of triplet halocarbenonitrenes 2-X, (X = F, Cl, and Br). All four compounds upon further irradiation undergo isomerization to substituted cyclopropenes 5-X (X = H, F, Cl, and Br), as suggested by their IR spectra.
间亚苯基偶联的碳氮烯（[(3-氮烯基苯基)亚甲基 (2-H)、(3-氮烯基苯基)氟亚甲基 (2-F)、(3-氮烯基苯基)氯亚甲基 (2-Cl)、(3-氮烯基苯基)溴亚甲基 (2-Br)]）已通过计算（采用B3LYP、MCSCF、CASPT2、ROMP2和QCISD(T)方法）和实验（采用红外、紫外和电子自旋共振光谱）进行了研究。对于每个物种，考虑了五个电子态。在探索的最高理论水平下，母体化合物（2-H）具有五重态基态，但其卤素衍生物（2-X，X = F、Cl和Br）具有三重态基态。发现2-X的Q[键]T能隙与相应苯基卡宾8-X的T-S能隙之间存在线性关系，这有助于合理化和预测间亚苯基连接的碳氮烯及类似物种的基态多重性。合成了用于光化学生成2-X（X = H、F、Cl和Br）的前体，并在低温下在基质（氩气、三醋精）中进行光解。红外（氩气，13 K）和电子自旋共振（三醋精，77 K）数据与三重态卤代碳氮烯2-X（X = F、Cl和Br）的生成相符。如红外光谱所示，所有四种化合物在进一步照射后都会异构化为取代环丙烯5-X（X = H、F、Cl和Br）。
