| In this paper, the molecular recognition and devices of crown ethers derivatives withalkali metal ions are theoretically studied. The following four systems are included.(1)Density functional theory study on a fluorescent chemosensor device of aza-crownether;(2)Theoretical study on supramolecular chemistry of alkali-metal cations withcrown ether derivatized thiophenes;(3)Theoretical study on cation complexation ofpyrene-and anthracene-appended crown ether derivatives;(4) Theoretical study on Na+binding properties of coumarin-crown ethers.Firstly, three derivatives of alkyl anthracene covalently bonded to aza-18-crown-6atthe nitrogen position, anthracene(CH2)n,(n=1-3) which act as an on-off fluorogenicphotoswitch have been theoretically studied using a computational strategy based ondensity functional theory. The binding energies, enthalpies and Gibbs free energies havebeen calculated for aza-18-crown-6(L) and their metal complexes. The fully optimizedgeometries have been performed with real frequencies which indicate the minima states.The natural bond orbital analysis is used to explore the interaction of host-guestmolecules. The absorption spectra differences between L and their metal ligands, theexcitation energies and absorption wavelength for their exited states have been studiedwith the basis set6-31+G(d,p). These fluorescent sensors and switchers based onphotoinduced electron transfer mechanism have been investigated. The PET process fromaza-crown ether to fluorophore can be suppressed or completely blocked by the entry ofalkali metal cations into the aza-crown ether-based receptor. Such a suppression of thePET process means that fluorescence intensity is enhanced. The binding selectivitystudies of the aza-crown ether part of L indicate that the presence of the alkali metalcations Li+, Na+and K+play an important role in determining the internal charge transferand the fluorescence properties of the complexes. In addition, the solvent effect has beeninvestigated.Secondly, this paper describes systemically a theoretical research on the interactionof alkali-metal cations (Li+, Na+, K+and Rb+) with five different crown ether derivatizedthiophenes using density functional theory. The fully optimized geometries have beenperformed with real frequencies which indicate the minima states. The optimizedstructures and electronic properties of the free ligands L (L1-L5), the complexes L/M+(Li+, Na+, K+and Rb+) have been performed at B3LYP/6-31+G(d,p) and Lanl2DZ level.Natural bond orbital and frequency analysis are discussed on the basic of the optimizedgeometric structures. The main driving forces of the coordination in host-guest molecules are investigated, the electron-donating O offers lone pair electrons to the contacting LP*(1-center valence antibond lone pair) of alkali-metal cations. In addition, the transitionenergies are performed by TD-DFT.Thirdly, pyrene-and anthracene-appended crown ether derivatives have beensynthesized by schiff’s base reaction. This paper describes systemically a theoreticalresearch on the interaction of cations (Na+, K+, Rb+, Cs+and NH4+) with three differentcrown ether derivatives using density functional theory. The fully optimized geometrieshave been performed with real frequencies which indicate the minima states. Theoptimized structures and electronic properties of the three ligands L (L1-L3), thecomplexes L/M+(Na+, K+, Rb+, Cs+and NH4+) have been performed atB3LYP/6-31G(d,p) and Lanl2DZ level. The IR spectra informs the interaction of thehost-guest molecules. Natural bond orbital and frequency analysis are discussed on thebasic of the optimized geometric structures. The main driving forces of the coordinationin host-guest molecules are investigated, the electron-donating O offers lone pairelectrons to the contacting LP*(1-center valence antibond lone pair) of alkali-metalcations. In addition, the transition energies are performed by TD-DFT.Lastly, a theoretical study of a series of coumarin-crown ethers and their complexeswith Na+is performed with the aid of DFT at B3LYP/6-31G(d,p) so as to obtain theoptimized structures and electronic properties. The fully optimized geometries have beenperformed with real frequencies which indicate the minima states. The structures andcoordination of the complexes are studied to identify the best match of thecoumarin-15-crown-5ethers with the cation Na+. Natural bond orbital and frequencyanalysis are discussed on the basic of the the stable conformers of the complexes. Themain driving forces of the coordination in host-guest molecules are investigated, theelectron-donating O offers lone pair electrons to the contacting LP*(1-center valenceantibond lone pair) of alkali-metal cation Na+. In addition, the transition energies areresearched by TD-DFT. |
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