物理化学学报
物理化學學報
물이화학학보
ACTA PHYSICO-CHIMICA SINICA
2009年
11期
2296-2304
,共9页
朱玥%蒲敏%何静%EVANS David G.
硃玥%蒲敏%何靜%EVANS David G.
주모%포민%하정%EVANS David G.
密度泛函理论%3'3'-偶氮苯磺酸%光异构化机理%激发态%势能面
密度汎函理論%3'3'-偶氮苯磺痠%光異構化機理%激髮態%勢能麵
밀도범함이론%3'3'-우담분광산%광이구화궤리%격발태%세능면
Density fuctional theory%3,3'-azobenzene sulphonate%Photoisomerization mechanism%Excited state%Potential energy profile
基于密度泛函理论(DVFT)中的B3LYP方法,在6-311++G(d,p)水平上全优化得到了3,3'-偶氮苯磺酸(3,3'-AbS)在S_0和T_1态顺反异构化机理.在S_0态存在两种异构化途径:绕角NNC反转和绕NC键旋转相结合的形式和单纯的绕CNNC二面角旋转形式,两种异构化途径的能垒分别为94.2和124.3 kJ·mol~(-1).有必要指出的是,在反转与旋转结合的途径上存在二次过渡态.在T_1态上仅存在旋转途径且其能垒为21.1 kJ·mol~(-1).采用含时密度泛函理论(TD-DFT),在B3LYP/6-311++(3(d,p)水平上,沿着基态的两种异构化途径计算得到了T_1,S_1,T_2和S_2态的垂直激发的势能剖面,分析了可能的光致异构化途径.当激发光波长为330 nm时,反应物分子被激发到S_2态,然后弛豫到较低的能态S_1发生异构化反应,旋转途径存在两条活化途径:(1)沿着S_1/S_0的圆锥交叉点衰变到产物;(2)由S_1态弛豫到T_1态后,在S_0-T_1-S_0的区域发生异构化,再转化到产物.计算结果表明,3,3'-AbS通过反转和旋转的结合形式实现在S_0态的异构化,而被激发后倾向于沿着旋转坐标作为其主要的异构化途径.
基于密度汎函理論(DVFT)中的B3LYP方法,在6-311++G(d,p)水平上全優化得到瞭3,3'-偶氮苯磺痠(3,3'-AbS)在S_0和T_1態順反異構化機理.在S_0態存在兩種異構化途徑:繞角NNC反轉和繞NC鍵鏇轉相結閤的形式和單純的繞CNNC二麵角鏇轉形式,兩種異構化途徑的能壘分彆為94.2和124.3 kJ·mol~(-1).有必要指齣的是,在反轉與鏇轉結閤的途徑上存在二次過渡態.在T_1態上僅存在鏇轉途徑且其能壘為21.1 kJ·mol~(-1).採用含時密度汎函理論(TD-DFT),在B3LYP/6-311++(3(d,p)水平上,沿著基態的兩種異構化途徑計算得到瞭T_1,S_1,T_2和S_2態的垂直激髮的勢能剖麵,分析瞭可能的光緻異構化途徑.噹激髮光波長為330 nm時,反應物分子被激髮到S_2態,然後弛豫到較低的能態S_1髮生異構化反應,鏇轉途徑存在兩條活化途徑:(1)沿著S_1/S_0的圓錐交扠點衰變到產物;(2)由S_1態弛豫到T_1態後,在S_0-T_1-S_0的區域髮生異構化,再轉化到產物.計算結果錶明,3,3'-AbS通過反轉和鏇轉的結閤形式實現在S_0態的異構化,而被激髮後傾嚮于沿著鏇轉坐標作為其主要的異構化途徑.
기우밀도범함이론(DVFT)중적B3LYP방법,재6-311++G(d,p)수평상전우화득도료3,3'-우담분광산(3,3'-AbS)재S_0화T_1태순반이구화궤리.재S_0태존재량충이구화도경:요각NNC반전화요NC건선전상결합적형식화단순적요CNNC이면각선전형식,량충이구화도경적능루분별위94.2화124.3 kJ·mol~(-1).유필요지출적시,재반전여선전결합적도경상존재이차과도태.재T_1태상부존재선전도경차기능루위21.1 kJ·mol~(-1).채용함시밀도범함이론(TD-DFT),재B3LYP/6-311++(3(d,p)수평상,연착기태적량충이구화도경계산득도료T_1,S_1,T_2화S_2태적수직격발적세능부면,분석료가능적광치이구화도경.당격발광파장위330 nm시,반응물분자피격발도S_2태,연후이예도교저적능태S_1발생이구화반응,선전도경존재량조활화도경:(1)연착S_1/S_0적원추교차점쇠변도산물;(2)유S_1태이예도T_1태후,재S_0-T_1-S_0적구역발생이구화,재전화도산물.계산결과표명,3,3'-AbS통과반전화선전적결합형식실현재S_0태적이구화,이피격발후경향우연착선전좌표작위기주요적이구화도경.
Photoisomerization pathways for 3,3'-azobenzene sulfonate (3,3'-AbS) in the S_0 and T_1 states were studied by using density functional theory (DFT) at the B3LYP/6-311++G(d,p) level. In the S_0 state, there are two isomerization pathways: the inversion of one NNC angle combined with the rotation around the NC bond and the rotation of the CNNC dihedral angle. The energy barriers of the two pathways are 94.2 and 124.3 kJ·mol~(-1), respectively. It is worthy to notice that there exist second-order transition states on the combination pathways of inversion and rotation. In the T_1 state, only the rotation pathway exists and its energy barrier is 21.1 kJ·mol~(-1). To investigate the photoisomerization pathway, the potential energy profiles of the vertical excitation for the excited states (T_1, S_1, T_2, and S_2) were calculated by time dependent density functional theory (TD-DFT) at the B3LYP/6-311++G(d,p) level along the two pathways. A photoexcitation at 330 nm results in the reactant molecule populating the S_2 state and then undergoing a rapid relaxation to the minimum of the S_1 state. Two possible isomerization pathways exist through the rotation pathway as follows: (1) the isomerization can easily occur through the S_0/S_1 conical intersection (CI) and descend to the S_0 state; (2) a relaxation to the T_1 state from the S_1 state may occur and the reaction can take place via the S_0-T_1-S_0 path. Calculation results show that the primary isomerization pathways for 3,3'-AbS are a combination pathway of inversion and rotation in the S_0 state and the rotation pathway when it is excited.
