Spectroscopy, NMR and DFT studies on molecular recognition of crown ether bridged chiral heterotrinuclear salen Zn(II) complex.
A barium-containing crown ether bridged chiral heterotrinuclear salen Zn(II) complex BaZn2L(ClO4)2, where L is a folded dinuclear chiral (R,R)-salen ligand, has been synthesized and characterized by elemental analysis, 1H NMR, UV-vis, IR, circular dichroism (CD) spectra, and mass spectra. As a folded dinuclear chiral host, its recognition with achiral guests (imidazole derivatives), rigid bidentate guest (1,4-diazobicyclo[2,2,2]octane, DABCO) and chiral guests (amino acid methyl esters) was investigated by means of UV-vis spectrophotometric titration, CD spectra. The association constants of D-amino acid methyl esters are found to be higher than those of their L-enantiomer. The sandwich-type binding of BaZn2L(ClO4)2-DABCO supramolecular assembly was specially studied via 1H NMR titration and 1H ROESY. To understand the recognition on molecular level, density functional theory (DFT) calculations on B3LYP/LanL2DZ were performed on the minimal energy conformations of host, guests, and host-guest complexes. The minimal energy conformations were obtained by molecular mechanics (MM) optimization and molecular dynamics (MD) simulation. The results of single point energy, HOMO energy, and charges transfer were analyzed. The results of theoretical calculations are in good agreement with the experimental data.
Gao
Feng
F
Department of Chemistry, Nankai University, Tianjin 300071, PR China.
Ruan
Wen-Juan
WJ
Chen
Jia-Mei
JM
Zhang
Ying-Hui
YH
Zhu
Zhi-Ang
ZA
D001464:Barium / Q000737:chemistry; D002942:Circular Dichroism; D043844:Crown Ethers / Q000138:chemical synthesis / Q000737:chemistry*; D005029:Ethylenediamines / Q000138:chemical synthesis / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D008968:Molecular Conformation; D013056:Spectrophotometry, Ultraviolet; D013237:Stereoisomerism; D017186:Titrimetry; D015032:Zinc / Q000737:chemistry*
D043844:Crown Ethers; D005029:Ethylenediamines; D001464:Barium; C011452:disalicylaldehyde ethylenediamine; D015032:Zinc