Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, United States.
J Am Chem Soc. 2010 Dec 1;132(47):16796-804. doi: 10.1021/ja909327z. Epub 2010 Nov 4.
The photochemistry of diphenylphosphoryl azide was studied by femtosecond transient absorption spectroscopy, by chemical analysis of light-induced reaction products, and by RI-CC2/TZVP and TD-B3LYP/TZVP computational methods. Theoretical methods predicted two possible mechanisms for singlet diphenylphosphorylnitrene formation from the photoexcited phosphoryl azide. (i) Energy transfer from the (π,π*) singlet excited state, localized on a phenyl ring, to the azide moiety, thereby leading to the formation of the singlet excited azide, which subsequently loses molecular nitrogen to form the singlet diphenylphosphorylnitrene. (ii) Direct irradiation of the azide moiety to form an excited singlet state of the azide, which in turn loses molecular nitrogen to form the singlet diphenylphosphorylnitrene. Two transient species were observed upon ultrafast photolysis (260 nm) of diphenylphosphoryl azide. The first transient absorption, centered at 430 nm (lifetime (τ) ∼ 28 ps), was assigned to a (π,π*) singlet S(1) excited state localized on a phenyl ring, and the second transient observed at 525 nm (τ ∼ 480 ps) was assigned to singlet diphenylphosphorylnitrene. Experimental and computational results obtained from the study of diphenyl phosphoramidate, along with the results obtained with diphenylphosphoryl azide, supported the mechanism of energy transfer from the singlet excited phenyl ring to the azide moiety, followed by nitrogen extrusion to form the singlet phosphorylnitrene. Ultrafast time-resolved studies performed on diphenylphosphoryl azide with the singlet nitrene quencher, tris(trimethylsilyl)silane, confirmed the spectroscopic assignment of singlet diphenylphosphorylnitrene to the 525 nm absorption band.
通过飞秒瞬态吸收光谱、光诱导反应产物的化学分析以及 RI-CC2/TZVP 和 TD-B3LYP/TZVP 计算方法研究了二苯膦酰叠氮的光化学。理论方法预测了从光激发的磷酸叠氮形成单重态二苯膦基氮烯的两种可能机制。(i) 能量从（π，π*）单重激发态转移到叠氮部分，从而导致单重激发态叠氮形成，随后分子氮失去形成单重态二苯膦基氮烯。(ii) 直接照射叠氮部分形成叠氮的激发单重态，后者继而失去分子氮形成单重态二苯膦基氮烯。二苯膦酰叠氮超快光解（260nm）时观察到两种瞬态物种。第一个瞬态吸收，中心位于 430nm（寿命（τ）∼28ps），被分配给一个位于苯基环上的（π，π*）单重 S(1)激发态，第二个在 525nm 处观察到的瞬态（τ∼480ps）被分配给单重二苯膦基氮烯。通过对二苯膦酰胺的研究获得的实验和计算结果，以及与二苯膦酰叠氮的结果一起，支持了从单重激发的苯基环向叠氮部分转移能量的机制，随后通过氮的排出形成单重膦基氮烯。用单重氮化物猝灭剂三（三甲基硅基）硅烷对二苯膦酰叠氮进行的超快时间分辨研究证实了单重二苯膦基氮烯对 525nm 吸收带的光谱分配。
