title: Influence of spiral framework on nonlinear optical materials.
abstract: A series of spiral donor-π-acceptor frameworks (i.e. 2-2, 3-3, 4-4, and 5-5) based on 4-nitrophenyldiphenylamine with π-conjugated linear acenes (naphthalenes, anthracenes, tetracenes, and pentacenes) serving as the electron donor and nitro (NO2 ) groups serving as the electron acceptor were designed to investigate the relationships between the nonlinear optical (NLO) responses and the spirality in the frameworks. A parameter denoted as D was defined to describe the extent of the spiral framework. The D value reached its maximum if the number of NO2 groups was equal to the number of fused benzene rings contained in the linear acene. A longer 4-nitrophenyldiphenylamine chain led to a larger D value and, further, to a larger first hyperpolarizability. Different from traditional NLO materials with charge transfer occurring in the one-dimensional direction, charge transfer in 2-2, 3-3, 4-4, and 5-5 occur in three-dimensional directions due to the attractive spiral frameworks, and this is of great importance in the design of NLO materials. The origin of such an enhancement in the NLO properties of these spiral frameworks was explained with the aid of molecular orbital analysis.
authors.affiliation: Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun 130024, Jilin (P.R. China); Institute of Theoretical and Simulational Chemistry, Academy of Fundamental and Interdisciplinary Sciences, Harbin Institute of Technology, Harbin 150080 (P.R. China).
authors.forename: Yang-Yang
authors.initials: YY
authors.lastname: Hu
authors.forename: Shi-Ling
authors.initials: SL
authors.lastname: Sun
authors.forename: Wen-Tao
authors.initials: WT
authors.lastname: Tian
authors.forename: Wei Quan
authors.initials: WQ
authors.lastname: Tian
authors.forename: Hong-Liang
authors.initials: HL
authors.lastname: Xu
authors.forename: Zhong-Min
authors.initials: ZM
authors.lastname: Su
mesh_terms: D000873:Anthracenes / Q000737:chemistry; D004159:Diphenylamine / Q000737:chemistry*; D004583:Electrons; D009281:Naphthalenes / Q000737:chemistry; D011789:Quantum Theory; D013329:Structure-Activity Relationship
chemical_list: D000873:Anthracenes; D009281:Naphthalenes; D004159:Diphenylamine
keywords: charge transfer; donor-acceptor systems; hyperpolarizability; nonlinear optics; spiral frameworks