Electronic Circular Dichroism of the Chiral Rigid Tricyclic Dilactam with Nonplanar Tertiary Amide Groups

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• 作者：Mark茅ta Pazderkov谩 ; V谩clav Profant ; Beata Seidlerov谩 ; Helena Dlouh谩 ; Jana Hoda膷ov谩 ; Tam谩s J谩vorfi ; Giuliano Siligardi ; Vladim铆r Baumruk ; Lucie Bedn谩rov谩 ; Petr Malo艌
• 刊名：Journal of Physical Chemistry B
• 出版年：2014
• 出版时间：September 25, 2014
• 年：2014
• 卷：118
• 期：38
• 页码：11100-11108
• 全文大小：302K
• ISSN：1520-5207

文摘

Electronic circular dichroism (ECD) of the spirocyclic dilactam 5,8-diazatricyclo[6,3,0,0^1,5]undecane-4,9-dione has been measured in the extended wavelength range (170鈥?60 nm) utilizing far-UV CD instrumentation including synchrotron radiation light source. The data of this model of two nonplanar tertiary amide groups interacting within the rigid chiral environment provided new information particularly about the shorter wavelength 蟺鈥撓€* transition region below 190 nm. The interpretation using TDDFT calculations confirmed that effects of amide nonplanarity follow our previous observations on monolactams as far as amide n鈭捪€* transitions are concerned. ECD band in the n鈭捪€* transition region of the nonplanar diamide exhibits an identical bathochromic shift and its sign remains tied to the sense of nonplanar deformation in the same way. As far as n鈭捪€* transitions are concerned amide nonplanarity acts as a local phenomenon independently reflecting sum properties of single amide groups. On the other hand, CD bands associated with 蟺鈥撓€* transitions (found between 鈭?70 to 210 nm) form an exciton-like couplet with the sign pattern determined by mutual orientation of the associated electric transition moments. This sign pattern follows predictions pertaining to a coupled oscillator. The influence of amide nonplanarity on 蟺鈥撓€* transitions is only minor and concentrates into the shorter wavelength lobe of the 蟺鈥撓€* couplet. The detailed analysis of experimental ECD with the aid of TDDFT calculations shows that there is only little interaction between effects of inherent chirality caused by nonplanarity of amide groups and amide鈥揳mide coupling. Consequently these two effects can be studied nearly independently using ECD. In addition, the calculations indicate that participation of other type of transitions (n鈭捪?, 蟺鈥撓? or Rydberg type transitions) is only minor and is concentrated below 180 nm.