Efficient acceptor groups for NLO chromophores: Competing inductive and resonance contributions in heterocyclic acceptors derived from 2-dicyanomethylidene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran

Karin Schmidt*, Stephen Barlow, Amalia Leclercq, Egbert Zojer, Sei Hum Jang, Seth R. Marder, Alex K.Y. Jen, Jean-Luc Bredas

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

38 Scopus citations

Abstract

The 2-dicyanomethylidene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF) group has been identified as a particularly strong acceptor suitable for the realization of highly efficient second-order NLO chromophores. To provide guidelines for a further improvement of heterocyclic acceptors, we present Sum-Over-States (SOS) calculations of second-order polarizabilities (β) for a series of donor-π-bridge-acceptor (D-π-A) chromophores. In particular, we investigate the effect of replacing the oxygen atom of the furan ring in TCF by a variety of other groups, X (SiH2, CH2, CCH 2, NH, CO, S, CCHNO2, SO, and SO2). Overall β is found to increase with the inductive electron-withdrawing character of X, with β being further increased or decreased when X has π-accepting or π-donating character. Within the framework of the two-level model, the effects associated with the π-donating and accepting character can be understood in terms of destabilizing and stabilizing effects on the lowest unoccupied molecular orbitals of the dipolar chromophores. When using the stronger 3-methyl-4-cyano-5-dicyanomethylidene-2-oxo-3-pyrroline (TCP) acceptor and replacing the pyrroline nitrogen atom with the same range of X groups, the inductive electron-withdrawing and π-accepting or π-donating characters of X have the same impact on β as in the TCF motif.

Original languageEnglish (US)
Pages (from-to)2944-2949
Number of pages6
JournalJournal of Materials Chemistry
Volume17
Issue number28
DOIs
StatePublished - Jan 1 2007

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Chemistry

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