Two-photon absorption (2PA) spectroscopy, a technique that measures the simultaneous absorption of two photons of light, was used to probe the formation of halogen-bonded complexes in solution. Halogen bonding is a type of charge-transfer interaction that often leads to charge-transfer transitions in the electronic absorption spectrum. Charge-transfer transitions typically have large 2PA cross-sections, therefore 2PA spectroscopy promises to provide a suitable method to probe halogen-bonded systems even when overlapping absorption bands in the traditional one-photon absorption (1PA) spectrum conceal the spectral changes due to complex formation. In order to demonstrate the feasibility of this method, we measured the 2PA spectrum of a model halogen bonding system with a broadband pump-probe technique using femtosecond laser pulses. The 2PA spectrum of the model complex has a charge-transfer band comparable to that observed in the 1PA spectrum, and that follows the expected concentration dependence of the complex.

Probing charge-transfer complexes with two-photon absorption spectroscopy

245th National Meeting (2013)

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