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Title: The Effect of Axial Mg{sup 2+} Ligation and Peripheral Hydrogen Bonding on Chlorophyll a

Abstract

Model systems of the chlorophyll a (Chla) molecule were studied using density functional theory. Dependence of structure variation of Chla on the polarity of ligand was described. The hydrogen bonding (H-bond) donated to the 13{sup 1}-keto carbonyl oxygen favors the ionic resonance structure of the 13{sup 1}-keto carbonyl bond. Such a H-bond causes spin density redistribution in anion, and charge transfer in cation from donor of H-bond to the porphyrin plane of Chla because of orbital admixing, which indicates that the spin density of chlorophyll cation could be easily regulated by its peripheral H-bond.

Authors:
; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab., Richland, WA (US), Environmental Molecular Sciences Laboratory (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
15011172
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Chemical Physics Letters; Journal Volume: 387; Journal Issue: 1-3; Other Information: PBD: 21 Mar 2004
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; BONDING; CARBONYLS; CATIONS; CHLOROPHYLL; FUNCTIONALS; HYDROGEN; OXYGEN; PORPHYRINS; RESONANCE; SPIN; ENVIRONMENTAL MOLECULAR SCIENCES LABORATORY

Citation Formats

Sun, Yuming, Wang, Hezhou, Zhao, Fuli, and Sun, Jinzuo. The Effect of Axial Mg{sup 2+} Ligation and Peripheral Hydrogen Bonding on Chlorophyll a. United States: N. p., 2004. Web. doi:10.1016/j.cplett.2004.01.103.
Sun, Yuming, Wang, Hezhou, Zhao, Fuli, & Sun, Jinzuo. The Effect of Axial Mg{sup 2+} Ligation and Peripheral Hydrogen Bonding on Chlorophyll a. United States. doi:10.1016/j.cplett.2004.01.103.
Sun, Yuming, Wang, Hezhou, Zhao, Fuli, and Sun, Jinzuo. 2004. "The Effect of Axial Mg{sup 2+} Ligation and Peripheral Hydrogen Bonding on Chlorophyll a". United States. doi:10.1016/j.cplett.2004.01.103.
@article{osti_15011172,
title = {The Effect of Axial Mg{sup 2+} Ligation and Peripheral Hydrogen Bonding on Chlorophyll a},
author = {Sun, Yuming and Wang, Hezhou and Zhao, Fuli and Sun, Jinzuo},
abstractNote = {Model systems of the chlorophyll a (Chla) molecule were studied using density functional theory. Dependence of structure variation of Chla on the polarity of ligand was described. The hydrogen bonding (H-bond) donated to the 13{sup 1}-keto carbonyl oxygen favors the ionic resonance structure of the 13{sup 1}-keto carbonyl bond. Such a H-bond causes spin density redistribution in anion, and charge transfer in cation from donor of H-bond to the porphyrin plane of Chla because of orbital admixing, which indicates that the spin density of chlorophyll cation could be easily regulated by its peripheral H-bond.},
doi = {10.1016/j.cplett.2004.01.103},
journal = {Chemical Physics Letters},
number = 1-3,
volume = 387,
place = {United States},
year = 2004,
month = 3
}
  • No abstract prepared.
  • Paramagnetic Ce(III), Pr(m), Nd(III), Sm(III), Eu(III), Tb(III), Dy(III), Ho(III), Er(III), Tm(III), and Yb(III) texaphyrins were studied in solution using [sup 1]H NMR spectroscopic techniques. Key spectroscopic features for the dinitrate complexes LnTx(NO[sub 3])[sub 2] were assigned on the basis of 1D NOE, COSY, and ROESY experiments as well as line width and isotropic shift analysis. The observed isotropic shifts can be fit to theoretical models, assuming dipolar contributions are dominant for all but the imino protons. The resulting calculated values are consistent with highly rhombic magnetic susceptibility tensors for those paramagnetic lanthanide texaphyrins in which one of the molecular magneticmore » axes is roughly perpendicular to the macrocycle plane. For the dinitrate complexes, a change in the magnetic anisotropy was observed between the Ho(ITI) and Er(III) texaphyrin complexes, a phenomenon that is considered reflective of the changes in metal-centered axial ligation that occur as the lanthanide series is transversed. Conformation of phosphate coordination in the solid state came from a single crystal X-ray diffraction analysis of the bis(diphenyl phosphate) adduct of Dy(III) texaphyrin. The Dy(III) ion is seven-coordinate with five donor atoms being provided by the texaphyrin ligand and two by monodentate diphenyl phosphate ions. The Dy(III) ion is only 0.073 A from the plane through the five nitrogen atoms of the macrocycle. 35 refs., 7 figs., 5 tabs.« less
  • This paper reports the molecular structure of the transition-metal tetrahydroborate complex Hf(BH/sub 4/)/sub 4/ by single-crystal neutron diffraction at 110 K. The compound crystallizes in the cubic space group P43m (T/sub d//sup 1/, No. 215) with a unit cell of dimensions a = 5.827 (4) angstrom. Full-matrix least-squares refinement gave a final value of R(F/sub 0//sup 2/) = 0.103 for 71 unique reflections with F/sub 0//sup 2/ > sigma(F/sub 0//sup 2/). The molecular structure consists of monomeric Hf(BH/sub 4/)/sub 4/ units having rigorously T/sub d/ symmetry and tridentate tetrahydroborate coordination. Important bond distances are Hf-B = 2.281 (8) angstrom, Hf-H(bridging)more » = 2.130 (9) angstrom, B-H(bridging) = 1.235 (10) angstrom, and B-H(terminal) = 1.150 (19) angstrom. Important bond angles are Hf-H(bridging)-B = 80.6 (6)/sup 0/, H(bridging)-B-H(bridging) = 105.8 (6)/sup 0/, and H(bridging)-B-H(terminal) = 112.9 (10)/sup 0/. It is seen that the internal BH/sub 4//sup -/ metrical parameters do not differ significantly from those in Hf(CH/sub 3/C/sub 5/H/sub 4/)/sub 2/(BH/sub 4/)/sub 2/, in which the tetrahydroborate ligands are coordinated in an unsymmetrical bidentate fashion. However, Hf-B is 0.17 (1) angstrom longer and Hf-H(bridging, average) 0.035 (9) angstrom shorter in the latter molecule.« less