Single and polycrystalline 4-hydroxycyanobenzene (4HCB) have been analyzed by means of both (UP) and linearly polarized (LP) infrared (IR) beams. Most of the signals found at room temperature (298 K) have been assigned to well defined vibrational modes. LP-IR investigations on single crystals (SCs) were carried out keeping the beam polarization aligned with either the a or the b axis of the crystal, delivering rather different responses. These differences are discussed in view of possible spatially anisotropic vibronic couplings between the benzenic -electrons and the molecule functional groups. In addition, signals suggesting the low concentration presence of tautomers within the crystal lattice were detected. Finally, LP-IR measurements of SCs in the temperature range between 298 and 120 K are reported and discussed, with particular reference to the hydrogen bonding-related functional groups of 4HCB. The so-obtained results allow to assign otherwise non clearly attributable OH bending signals. In addition, they i) indicate a possible anisotropic shrinking of the crystals upon temperature decrease, and ii) point to a non-negligible vibronic coupling between the -electrons of the functional groups involved in the hydrogen bond and those belonging to the benzenic ring, suggesting the use of LP-IR as a valuable tool for non-contact, non-destructive characterization of the electronic behavior of organic semiconductors.
Infrared Investigations of 4-Hydroxycyanobenzene Single Crystals
FRABONI, BEATRICE;TESSAROLO, MARTA;
2013
Abstract
Single and polycrystalline 4-hydroxycyanobenzene (4HCB) have been analyzed by means of both (UP) and linearly polarized (LP) infrared (IR) beams. Most of the signals found at room temperature (298 K) have been assigned to well defined vibrational modes. LP-IR investigations on single crystals (SCs) were carried out keeping the beam polarization aligned with either the a or the b axis of the crystal, delivering rather different responses. These differences are discussed in view of possible spatially anisotropic vibronic couplings between the benzenic -electrons and the molecule functional groups. In addition, signals suggesting the low concentration presence of tautomers within the crystal lattice were detected. Finally, LP-IR measurements of SCs in the temperature range between 298 and 120 K are reported and discussed, with particular reference to the hydrogen bonding-related functional groups of 4HCB. The so-obtained results allow to assign otherwise non clearly attributable OH bending signals. In addition, they i) indicate a possible anisotropic shrinking of the crystals upon temperature decrease, and ii) point to a non-negligible vibronic coupling between the -electrons of the functional groups involved in the hydrogen bond and those belonging to the benzenic ring, suggesting the use of LP-IR as a valuable tool for non-contact, non-destructive characterization of the electronic behavior of organic semiconductors.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
