Theoretical Investigations of the Effects of J-Aggregation on the Linear and Nonlinear Optical Properties of E-4-(4-Dimethylaminostyryl)-1-methylpyridinium [DAMS+]
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- 作者：Francesca Nunzi ; Simona Fantacci ; Filippo De Angelis ; Antonio Sgamellotti ; Elena Cariati ; Renato Ugo ; Piero Macchi
- 刊名：Journal of Physical Chemistry C
- 出版年：2008
- 出版时间：January 31, 2008
- 年：2008
- 卷：112
- 期：4
- 页码：1213 - 1226
- 全文大小：540K
- 年卷期：v.112,no.4(January 31, 2008)
- ISSN：1932-7455
文摘
J-type aggregation of organic chromophores into inorganic host matrixes provides a useful route towardmaterials showing strong second-order nonlinear optical (NLO) response. The increased NLO response ofJ-aggregates is related to the peculiar arrangement of the NLO-phores into the host matrix, which producesthe appearance of a narrow and intense band in the material electronic absorption spectrum, red-shifted withrespect to the main absorption band of the isolated NLO-phore. A theoretical investigation, based on DFT,TDDFT, and ZINDO calculations on the relationship between the structural features of various [DAMS+]([DAMS+] = E-4-(4-dimethylaminostyryl)-1-methylpyridinium) dimeric or oligomeric aggregates and theirlinear and nonlinear optical properties shows that the appearance of a new red-shifted absorption band, typicalof J-aggregation, is associated with interchromophoric transitions of charge-transfer character, due to thesplitting of HOMO and LUMO levels. The intensity of this latter band increases by increasing the number ofNLO-phores in a model of oligomeric arrangement of J-aggregates. The calculated quadratic hyperpolarizabilities for the mostly responsive J-type trimeric aggregates of [DAMS+] are found to largely exceed that ofthree isolated NLO-phores, confirming a cooperative NLO strong contribution due to J-aggregation. Finally,our DFT and TDDFT calculations on eclipsed or with opposite dipole dimeric H-aggregates of [DAMS+]show a splitting of HOMO and LUMO levels, which gives place to interchromophoric transitions of charge-transfer character but blue-shifted, as observed experimentally.