Theoretical Study of Effects of Anchoring Groups on Photovoltaic Properties of a Triarylamine-Based p-Type Sensitizer.

The effects of anchoring groups on triarylamine-based p-type dyes were studied by substituting the strong electron-withdrawing carboxyl group with the weak electron-withdrawing pyridyl and the electron-rich catechol groups. Judged by the index t, the charge separation would be improved greatly when the carboxyl group of P4 is replaced by the pyridyl or catechol groups. Although carboxyl as an anchoring group lowers the HOMO energy and facilitates the hole injection in comparison with pyridyl and catechol groups, the weak electron-withdrawing pyridyl and the electron-rich catechol groups facilitate the charge separation. E g becomes narrow as the electron-withdrawing abilities of the anchoring groups decrease or as the conjugation extends. Both the extended π-spacers and the substitution of carboxyl with pyridyl and catechol groups promote the redshifts of adsorption wavelengths. The oscillator strengths for all dyes are over 2.00, indicating that all the dyes are able to harvest the sunlight strongly. The ΔG CR values of P4, DF4, and DZ4 are smaller than those of the other dyes. Also, these dyes have larger adsorption over infrared visible light, indicating that these dyes may be good candidates for p-type DSSCs.

IR Spectra of Different O2-Content Hemoglobin from Computational Study: Promising Detector of Hemoglobin Variant in Medical Diagnosis.

IR spectra of heme and different O2-content hemoglobin were studied by the quantum computation method at the molecule level. IR spectra of heme and different O2-content hemoglobin were quantificationally characterized from 0 to 100 THz. The IR spectra of oxy-heme and de-oxy-heme are obviously different at the frequency regions of 9.08-9.48, 38.38-39.78, 50.46-50.82, and 89.04-91.00 THz. At 24.72 THz, there exists the absorption peak for oxy-heme, whereas there is not the absorption peak for de-oxy-heme. Whether the heme contains Fe-O-O bond or not has the great influence on its IR spectra and vibration intensities of functional groups in the mid-infrared area. The IR adsorption peak shape changes hardly for different O2-content hemoglobin. However, there exist three frequency regions corresponding to the large change of IR adsorption intensities for containing-O2 hemoglobin in comparison with de-oxy-hemoglobin, which are 11.08-15.93, 44.70-50.22, and 88.00-96.68 THz regions, respectively. The most differential values with IR intensity of different O2-content hemoglobin all exceed 1.0 × 104 L mol-1 cm-1. With the increase of oxygen content, the absorption peak appears in the high-frequency region for the containing-O2 hemoglobin in comparison with de-oxy-hemoglobin. The more the O2-content is, the greater the absorption peak is at the high-frequency region. The IR spectra of different O2-content hemoglobin are so obviously different in the mid-infrared region that it is very easy to distinguish the hemoglobin variant by means of IR spectra detector. IR spectra of hemoglobin from quantum computation can provide scientific basis and specific identification of hemoglobin variant resulting from different O2 contents in medical diagnosis.

Density functional theory study on (LiNH2)n (n=1-5) clusters.

Geometrical structures and relative stabilities of (LiNH(2))(n) (n = 1-5) clusters were studied using density functional theory (DFT) at the B3LYP/6-31G* and B3LYP/6-31++G* levels. The electronic structures, vibrational properties, N-H bond dissociation energies (BDE), thermodynamic properties, bond properties and ionization potentials were analyzed for the most stable isomers. The calculated results show that the Li-N and Li-Li bonds can be formed more easily than those of the Li-H or N-H bonds in the clusters, in which NH(2) is bound to the framework of Li atomic clusters with fused rings. The average binding energies for each LiNH(2) unit increase gradually from 142 kJ mol(-1) up to about 180 kJ mol(-1) with increasing n. Natural bond orbital (NBO) analysis suggests that the bonds between Li and NH(2) are of strong ionicity. Three-center-two-electron Li-N-Li bonding exists in the (LiNH(2))(2) dimer. The N-H BDE values indicate that the change in N-H BDE values from the monomer a1 to the singlet-state clusters is small. The N-H bonds in singlet state clusters are stable, while the N-H bonds in triplet clusters dissociate easily. A study of their thermodynamic properties suggests that monomer a1 forms clusters (b1, c1, d2 and e1) easily at low temperature, and clusters with fewer numbers of rings tend to transfer to ones with more rings at low temperature. E(g), E(HOMO) and E(av) decrease gradually, and become constant. Ring-like (LiNH(2))(3,4) clusters possess higher ionization energy (VIE) and E(g), but lower values of E(HOMO). Ring-like (LiNH(2))(3,4) clusters are more stable than other types. A comparison of structures and spectra between clusters and crystal showed that the NH(2) moiety in clusters has a structure and spectral features similar to those of the crystal.