Low-wavenumber Vibrations Research Articles

High temperature Raman spectroscopic analysis of the crystal growth of Bi2ZnOB2O6

Micromechanism of crystal growth has received considerable attention as a fundamental subject. However, in situ observation of the crystal growth process remains challenging. In this study, high-temperature Raman spectroscopy has been utilized to investigate the growth pattern of Bi2ZnOB2O6 crystals via in situ exploration of the starting solution structure near the crystal–solution interface. The experimental results show that the solution primarily consists of ZO4 and BO3 units corresponding to 370, 539, 664, and 1293 cm−1 vibration frequencies. These units connect with each other forming longer chains in the area close to the crystal, and they are related to the presence of low-wavenumber vibrations in the Raman spectrum. Furthermore, a loose embryonic structure of the Bi2ZnOB2O6 crystal is observed near the crystal–solution interface owing to the formation of Bi–O bonds. Therefore, this study successfully provides a clear understanding of the formation mechanism of Bi2ZnOB2O6 crystals.

ChemInform Abstract: Vibrational Spectra, Force Field and Normal Modes of 4,13-Diaza-18- crown-6.

Abstract Raman and IR spectra of uncomplexed 1,7,10,16-tetraoxa-4,13-diazacyclooctadecane (4,13-diaza18-crown-6) have been measured in the solid state. Normal coordinate calculations have been carried out on the C2h conformation of this macrocyclic compound. The force field of the diazacrown ether has been determined by adjusting several important several force constants associated with the imino group, other force constants being constrained, as transferred, to those of 18-crown-6. The vibrational assignments of 4,13-diaza-18-crown-6 are made on the basis of the previous assignments of a KSCN complex of 18-crown-6 with a similar ring conformation and of the results of the normal coordinate calculations. The normal modes of low-wavenumber vibrations are depicted. The lowest two vibrations represent out-of-plane deformations of folding the macrocyclic ring double. These modes are favourable to complexation of the macrocycle with guest. It is likely that these low-wavenumber vibrations are possible paths of the inclusion of the guest by the macrocyclic ring.

The behavior of hydroxyl units of synthetic goethite and its dehydroxylated product hematite

The behavior of the hydroxyl units of synthetic goethite and its dehydroxylated product hematite was characterized using a combination of Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) during the thermal transformation over a temperature range of 180–270°C. Hematite was detected at temperatures above 200°C by XRD while goethite was not observed above 230°C. Five intense OH vibrations at 3212–3194, 1687–1674, 1643–1640, 888–884 and 800–798 cm −1, and a H 2O vibration at 3450–3445 cm −1 were observed for goethite. The intensity of hydroxyl stretching and bending vibrations decreased with the extent of dehydroxylation of goethite. Infrared absorption bands clearly show the phase transformation between goethite and hematite; in particular, the migration of excess hydroxyl units from goethite to hematite. Two bands at 536–533 and 454–452 cm −1 are the low wavenumber vibrations of FeO in the hematite structure. Band component analysis data of FTIR spectra support the fact that the hydroxyl units mainly affect the a plane in goethite and the equivalent c plane in hematite.

Vibrational spectra, force field and normal modes of 4,13-diaza-18-crown-6

Raman and IR spectra of uncomplexed 1,7,10,16-tetraoxa-4,13-diazacyclooctadecane (4,13-diaza18-crown-6) have been measured in the solid state. Normal coordinate calculations have been carried out on the C 2h conformation of this macrocyclic compound. The force field of the diazacrown ether has been determined by adjusting several important several force constants associated with the imino group, other force constants being constrained, as transferred, to those of 18-crown-6. The vibrational assignments of 4,13-diaza-18-crown-6 are made on the basis of the previous assignments of a KSCN complex of 18-crown-6 with a similar ring conformation and of the results of the normal coordinate calculations. The normal modes of low-wavenumber vibrations are depicted. The lowest two vibrations represent out-of-plane deformations of folding the macrocyclic ring double. These modes are favourable to complexation of the macrocycle with guest. It is likely that these low-wavenumber vibrations are possible paths of the inclusion of the guest by the macrocyclic ring.

The [formula omitted] single vibronic level fluorescence spectrum of styrene vapor

Single vibronic level (SVL) fluorescence spectra following excitation into the 0 0 0 band and many sequence and cross-sequence bands in the A ̃ 1A′- X ̃ 1A′ system of styrene have been recorded and assigned. The technique is shown to be very powerful in obtaining accurate energy levels for low-wavenumber vibrations, particularly in the X ̃ state, where it is capable of giving information regarding vibrational levels inaccessible by conventional infrared or Raman spectroscopy. Interpretation of the spectra leads to many new assignments in the absorption spectrum and to an accurate knowledge of many vibrational energy levels. An important reassignment is that of the 41 0 142 0 1 band previously assigned to 40 0 2 ( ν 40, ν 41, and ν 42 are all a″ vibrations). The two most important pieces of information which derive from analysis of the SVL spectra are (a) the first five vibrational levels of ν 42, the C(1)- C( α) torsional vibration, in the X ̃ state, each accurate to about ±0.2 cm −1, and (b) the fact that the normal coordinates of ν 42 and ν 41, an out-of-plane substituent vibration, are very heavily mixed in the A ̃ , relative to the X ̃ , state—an extreme case of the Duschinsky effect. As a result of analysis of the SVL spectra, analysis of the absorption spectrum is now so complete that we can be confident that the Hui and Rice proposal that the CH 2 group of the substituent is perpendicular to the plane of the rest of the molecule in the A ̃ state has no evidence to support it.

Intramolecular easily polarizable N+H ⋯ N hydrogen bonds with NN′-dipiperidylalkane perchlorates. Proton magnetic resonance and infrared investigations

Five NN′-dipiperidylalkanes were prepared and their perchlorates were studied in [2H3]acetonitrile solutions by p.m.r. and i.r. spectroscopy. Structurally symmetrical N+H ⋯ N ⇌ N ⋯ H+N hydrogen bonds are formed if such formation is not sterically hindered. The symmetry of the potential in these hydrogen bonds makes them easily polarizable. In contrast to results with intermolecular bonds no continuum is, however, observed since, first, the distribution of the hydrogen bond lengths is narrower for intramolecular than for intermolecular hydrogen bonds and secondly, these N+H ⋯ N ⇌ N ⋯ H+N hydrogen bonds are screened against the local electrical fields and against coupling with low wavenumber vibrations in their environment by the piperidine rings.

The vibrational spectra and structure of organogermanes. VII. Low-wavenumber vibrations of some diphenyl-germanes

The IR spectra of the series (C 6H 5) 2GeX 2 (where X is H, D, Cl and Br) have been recorded from 4000 to 33 cm −1. The Raman spectra of the liquids have also been recorded and depolarization values measured. The spectral region below 900 cm −1 has been interpreted in detail and the phenyl vibrations assigned assuming C 2v local ring symmetry. It has been possible to make consistent assignments for the low-wavenumber vibrations for the four molecules and these are consistent with previous investigations of similar diphenylsilane and diphenylstannane molecules.

The vibrational spectra and structure of organogermanes-V

The infrared spectra of the series (C 6 H 5 ) 3 GeX (where X is bromine, chlorine, fluorine, hydrogen and deuterium) have been recorded from 4000 to 33 cm −1 . The Raman spectra have also been recorded and depolarization values have been measured for the chloride, hydride and deuteride. The spectral region below 700 cm −1 have been interpreted in detail for all five molecules and the complete assignments are given for the hydride and deuteride to 3200 cm −1 . The assignments are based on previous data for phenylgermanes and other monosubstituted benzenes as well as Raman depolarization values where they have been measured. It has been possible to make consistent assignments for the low wavenumber vibrations for the five molecules and the assignments are in agreement with previous investigations for the similar triphenylsilane and triphenylstannane molecules.