Improper blue-shifting

B. Reimann, K. Buchhold, S. Vaupel, B. Brutschy, Z. Havlas, V. Spirko, and P. Hobza, Improper, Blue-shifting hydrogen bond between fluorobenzene and fluoroform, J. Phys. Chem. A 105, 5560-5566 (2001). 

W. Zierkiewicz, D. Michalska, Z. Havlas, and P. Hobza, Study of the nature of improper blue-shifting hydrogen bonding and standard hydrogen bonding in the XsCH- -OH and XH- -0H2 complexes (X = F, Cl, Br, I) a correlated ah initio study, Chem. Phys. Chem. 3, 511-518 (2002). 

Van der Veken, B.J., Herrebout, W.A., Szostak, R., Shchepkin, D.N., Havlas, Z., and Hobza, P., The nature of improper blue-shifting hydrogen bonding verified experimentally, J. Am. 

Figure 12.19 Factors responsible for structural and spectroscopic consequences of H-bond formation. Different dominating effects give "normal" red-shifted H-bonds and "improper" blue-shifted H-bonds.

Farid 88) did not report on the excimer lifetime of the pyrene compound in the systems that were studied. Nevertheless, they proposed that the blue shift of the excimer emission peak in glassy polymers relative to solution was due to improper orientation of the excimer components in the polymer matrix 88). This proposal is supported by the observation 88) that the blue shift of the excimer peak for the pyrene... 

A. J. Barnes, Blue-shifting hydrogen bonds—are they improper or proper J. Mol. Struct. 704, 3-9 (2004). 

Blue-shifted H-bonds The reversal of the trademark behavior of H-bonds is the seemingly paradoxical C-H bond shortening and the blue-shift in the respective IR stretching frequency observed in the so-called improper or blue-shifting H-bonds. This behavior reflects rehybridization as the second structural force... 

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