Thermally induced rearrangement of hydrogen-bonded helices in solid 4-isopropylphenol as studied by calorimetric, proton NMR, dielectric and near IR spectroscopic methods

Molecular motions contributions to optical nonlinearity of N-benzyl-2-methyl-4-nitroaniline studied by temperature-dependent FT-IR, 1H NMR spectroscopy and DFT calculations

“…The Raman excitation profiles of lattice Table 2 The calculated and experimentally obtained values of second moment of 1 H NMR line (M 2 ) in BNA solid for rigid structure, methyl, phenyl group rotations and trans-gauche motion of methylene group. The M 2 values in the m-NA, MNA and 4-IP crystals are given for comparison [8,15,16]. Note that M 2 value for m-NA was given for -NH 2 180°p roton jumps.…”

“…The calculated and experimentally estimated second moment in BNA solid for different models (with inter-, intra-molecular and total contributions) are collected in Table 2 together with the M 2 data for m-NA, MNA and 4-IP crystals for comparison (M 2 value for m-NA was found for -NH 2 180°proton jumps) [8,15,16]. The calculated M 2 value for rigid lattice in 4-IP crystal (where two energetically inequivalent methyl groups are present) is similar to BNA and amounts to 22.54 Â 10 À8 T 2 while experimental value is much lower and equals to 15.7 Â 10 À8 T 2 at 100 K [16].…”

“…The earlier studies showed that the charged polarons (radical anions), dynamic disorder of phenyl ring and both (three) nitro and amine (methyl) substituents leads to the instantaneous helical superstructure in the m-NA [3,4] (MNA [6,15]) and contribute to the SHG in these crystals. It was found by the 1 H NMR method that methyl group rotations are dominant motions in the solid MNA and 4-IP at about 90 K and 100 K, respectively [15,16]. It is worth to add that the charged polarons were also detected in the 4-IP crystals [16].…”

“…It was found by the 1 H NMR method that methyl group rotations are dominant motions in the solid MNA and 4-IP at about 90 K and 100 K, respectively [15,16]. It is worth to add that the charged polarons were also detected in the 4-IP crystals [16].…”

“…This work is a continuation of studies on optically nonlinear (NLO) benzene derivatives crystals such as meta-nitroaniline (m-NA) [3,4,8], 2-methyl-4-nitroaniline (MNA) [6,14,15], 4-isopropylphenol (4-IP) [16] and N-benzyl-2-methyl-4-nitroaniline (BNA) [7,17,18]. The earlier studies showed that the charged polarons (radical anions), dynamic disorder of phenyl ring and both (three) nitro and amine (methyl) substituents leads to the instantaneous helical superstructure in the m-NA [3,4] (MNA [6,15]) and contribute to the SHG in these crystals.…”