Chromium tricarbonyl complexes η6-bonded to 3-amino-9-ethylcarbazole at either the NH2-substituted aryl ring (1) or the unsubstituted aryl ring (2) have been synthesized and their UV-visible absorption spectra determined. In comparison to 2, 1 causes a subtle blue shift in the metal-to-ligand charge-transfer band along with spectral shape changes due to electron transfer from the NH2 substituent to the Cr(CO)3 center.

We used two-dimensional (2D) correlation infrared spectroscopy to study further the potassium-induced conformation transition in Nephila spidroin films. It provided increased resolution and important new information on the sequence of events in the conformation transition process, showing that â-sheet formed from the helical component before they formed from random coil. It also showed more evidence that formation of the 1691cm-1 (turn/bend) peak did not proceed with the same kinetics as the 1620cm-1 (antiparallel â-sheet component) one, so we attribute the 1691cm-1 peak to turns which formed with different kinetics as the antiparallel β-sheets. We present a single coherent and detailed hypothesis for the assembly and secondary structural transition of silk proteins in vivo and in vitro based on our findings and on evidence from other laboratories.

Raman spectra of a polythiophene film measured over a temperature range 298-98K were analyzed using generalized two-dimensional correlation spectroscopy. In the 1600-1250cm-1 region, the asynchronicity of the bands indicates the existence of different species in the investigated polythiophene sample. At least four distinct bands at 1485, 1454, 1418, and 1360cm-1 were identified. Among them, the band at 1454cm-1, attributed to the neutral species of PTh, is found to be sensitive to the temperature-induced structural changes of the polythiophene film, while the bands of the oxidized species are less sensitive to the temperature change during the cooling process.

In this study, the diffusion process of water molecules in poly(є-caprolactone) (PCL) has been investigated using in-situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. In our system, the original broad water OH bands in 1D IR spectra can be effectively differentiated into four bands, located at 3641, 3593, 3410, and 3203cm-1, respectively, using 2D correlation analysis. The bands at 3641cm-1 (antisymmetric) and 3593cm-1 (symmetric) are assigned to the OH stretching vibration of water partially hydrogen bonded with hydrophilic carbonyl group (CvO) of PCL, while the other band pair at 3410cm-1 (antisymmetric) and 3203cm-1 (symmetric) could be attributed to the stretching vibration of water fully hydrogen bonded with another water molecule. According to the result of the asynchronous correlation, it was concluded that the water molecules at first diffuse into free volume (microvoids) or are molecularly dispersed into the PCL matrix and then form hydrogen bond with the CvO group of the polymer during the process of water diffusion. In addition, the diffusion coefficient was estimated using nonlinear curve fitting of OH band areas in the range of 3800-3000cm-1.

A recently developed technique, i.e., two-dimensional infrared (2D IR) correlation spectroscopy, is used to study the thermal behavior of poly(ethylene-co-vinyl alcohol)-graft-poly(-caprolactone), a new synthesized highly grafted copolymer. The use of the 2D IR approach to analyze temperature-dependent spectra collected in situ during the temperature elevation process effectively enhanced the spectral resolution and revealed details on the hydrogen bonding and conformational change which are not easily detected in the traditional one-dimensional spectra. The sequence of the spectral changes of different OH and CH2 fundamental vibrations during heating the polymer was inferred from the signs of the asynchronous peaks. Evidence that the conformational changes of the methylene groups precede the loosening of hydrogen bonds is provided.