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Published August 25, 2004 | public
Journal Article

Contrasting Linear and Quadratic Nonlinear Optical Behavior of Dipolar Pyridinium Chromophores with 4-(Dimethylamino)phenyl or Ruthenium(II) Ammine Electron Donor Groups

Abstract

In this article, we contrast the optical properties of dipolar chromophores having 4-(dimethylamino)phenyl electron donor (D) and pyridinium acceptor (A) groups with those of closely related cations having pyridyl-coordinated RuII donors. A range of physical data, including that from Stark (electroabsorption) spectroscopy, permits unprecedented quantitative comparisons, most notably regarding the effects of extension of bridging polyene chains. The purely organic compounds display normal optical properties in that their intense, visible π → π* intramolecular charge-transfer (ICT) bands red-shift as the number of E-ethylene units (n) increases from 1 to 3 and the associated static first hyperpolarizabilities β_0 increase steadily with n. The related RuII complexes show intense, visible d → π* metal-to-ligand charge-transfer (MLCT) bands, which are found to lower energy when compared with the ICT transitions of the corresponding organics. Abnormally, these MLCT bands blue-shift as n increases, and β_0 maximizes at n = 2. Time-dependent density-functional theory and finite field calculations verify these empirical trends for both types of compound, which can be rationalized as arising from the differing orbital structures of the chromophores and the associated degrees of D−A electronic coupling.

Additional Information

© 2004 American Chemical Society. Received April 23, 2004, Publication Date (Web): August 3, 2004. We thank the EPSRC for support (a studentship and Grants GR/M93864 and GR/R54293) and also MCyT-FEDER (BQU2002-00219) and Gobierno de Aragon-Fondo Social Europeo (P009-2001 and E39). This research was partially carried out at Brookhaven National Laboratory under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy and supported by its Division of Chemical Sciences, Office of Basic Energy Sciences.

Additional details

Created:
August 19, 2023
Modified:
October 25, 2023