Oscillatory polarons generation by near IR and spin induced chirality studies in optically nonlinear 1,3-dinitrobenzene crystal

• Published in: Optical materials Vol. 35; no. 5; pp. 1004 - 1012
• Main Authors: Magdalena Szostak, M., Chojnacki, Henryk, Piela, Katarzyna, Bidzińska, Ewa, Dyrek, Krystyna
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier B.V 01.03.2013; Elsevier
• Subjects: Anions; Atomic and molecular physics; Autocatalytic process; Band spectra; Chirality; Circular dichroism spectra; Compact disks; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Crystals; Density; Dichroism; Electron states; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Hydrogen bond; Mathematical analysis; Molecular properties and interactions with photons; Near IR conductivity band; Nonlinear optical crystals; Optical activity and dichroism; magnetooptical and electrooptical spectra; Optical activity, optical rotation; circular dichroism; Optical materials; Optics; O⋯O interactions; Physics; Polarons and electron-phonon interactions; Polymers and organics; Circular dichroism spectra; Autocatalytic process; O⋯O interactions; Near IR conductivity band; Hydrogen bond; Band structure; Electronic properties; Non linear material; O···O interactions; Laser beams; Intramolecular charge transfer; Circular dichroism; Hydrogen bonds; Ionization; Electric hyperpolarizability; Optical materials; Dipole moments; Absorption spectra; EPR spectra; Polarons; Crystal structure
• ISSN: 0925-3467; 1873-1252
• DOI: 10.1016/j.optmat.2012.12.010

[Display omitted] ► Unexpectedly, the circular dichroism spectra of 1,3-dinitrobenzene were recorded. ► NIR irradiations caused temporal fluctuations of EPR signals. ► Quantum chemical calculations confirmed the chirality of mDNB radical anion. ► Polarons concentration fluctuations suggests mDNB autocatalytic reduction by NIR. ► Polarons and helical packing seem to contribute to mDNB optical nonlinearity. Paramagnetic species in the 1,3-dinitrobenzene (mDNB) crystal have been detected by EPR spectroscopy and the intervalence (conductivity) band at ∼10,400cm−1 along the polar c axis, and the band at ∼7400cm−1 along the a axis, of unknown origin, have been found in its polarized NIR spectra. The radical anions occurrence and supposed helical superstructure formed due to nitro groups interactions have induced the chirality of solid mDNB confirmed by the CD spectra record and ab initio quantum chemical calculations. The several times irradiation of mDNB crystal samples by the 980nm and 1550nm laser diode beams have revealed temporal fluctuations of radical anions concentration (EPR) and of NIR band intensities, as well as CD spectra changes. An autocatalytic reduction by NIR is supposed to be responsible for the observed fluctuations. The proposed conclusions were reinforced by the density functional (DFT) calculations of electronic properties (ionization energy, electron affinity, dipole moment, hyperpolarizability) of mDNB neutral and charged clusters formed along the hypothetical helix and by the calculation of crystal band structure. The UV–Vis–NIR absorption and CD spectra of mDNB molecular systems were computed at non-empirical all-electron level by DFT method within the correlation consistent 6-311G**(2d,2p) basis set and hybrid B3LYP density functional.