Large Dipolar Spin鈥揝pin Interaction in a Photogenerated U-Shaped Triradical

详细信息    查看全文

• 作者：Daniel M. Gardner ; Hsiao-Fan Chen ; Matthew D. Krzyaniak ; Mark A. Ratner ; Michael R. Wasielewski
• 刊名：Journal of Physical Chemistry A
• 出版年：2015
• 出版时间：July 23, 2015
• 年：2015
• 卷：119
• 期：29
• 页码：8040-8048
• 全文大小：496K
• ISSN：1520-5215

文摘

Transient electron paramagnetic resonance (TREPR) spectroscopy has been used to study the spin鈥搒pin interactions in a novel U-shaped electron donor鈥揷hromophore鈥揳cceptor鈥搑adical (D鈥揅鈥揂鈥揜^{鈥?/sup>) system in which a xanthene bridge holds a tert-butylphenyl nitroxide (BPNO鈥?/sup>) radical in close proximity to a naphthalene-1,8:4,5-bis(dicarboximide) (NDI) acceptor. Photoexcitation of the 4-aminonaphthalene-1,8-dicarboximide (ANI) chromophore results in rapid, two-step electron transfer to generate the triradical (D+鈥?/sup>鈥揅鈥揂鈥撯€?/sup>鈥揜鈥?/sup>). The large through-bond distance between A鈥撯€?/sup> and R鈥?/sup> makes their spin鈥搒pin exchange interaction (2J_AR) negligibly small, whereas their short through-space distance results in a strong dipolar interaction (D_AR), which is observed as a set of broad lines in the TREPR spectra of D+鈥?/sup>鈥揅鈥揂鈥撯€?/sup>鈥揜鈥?/sup> in solid toluene solution at 85 K. Transient nutation experiments show that these transitions belong to a species with spin S = 1, whereas experiments on D+鈥?/sup>鈥揅鈥揂鈥撯€?/sup>鈥揜鈥?/sup> in the oriented nematic liquid crystal 4-cyano-4鈥?n-pentylbiphenyl at 85 K demonstrate the anisotropy of D_AR.}