Theoretical Study On A Seriers Of Calixarene Compounds Molecular Recognition And Supramolecular Devices

Currently, molecular recognition and supramolecular devices are one of thehottest topics in supramolecular chemistry. The current paper systematically studiedthe following four calixarene compound systems using the quantum chemistrymothods:(1) complexation of alkali-metal cations by conformationally rigid,stereoisomeric calix[4]arene crown ethers;(2) computational investigation of a newion-pair receptor for calix[4]pyrrole;(3) computational investigations into newfluorescence quenching process induced by complexation of alkali metal ion;(4)theoretical study on conformational features and cation-binding properties of adiquinone calix[4]arene.Firstly, the quantum mechanical study of the cone, partial-cone, and1,3-alternate1,3-diethoxy-p-tert-butylcalix[4]crown-5and their interaction with thealkali metal cations (Na~+, K~+, and Rb~+) has been performed. Geometries, bindingenergies, and binding enthalpies are evaluated at the restricted hybrid Becke’s threeparameter exchange functional (B3LYP) level using standard6-31G basis set andrelativistic effective core potentials. The optimized geometric structures are used toperform natural bond orbital (NBO) analysis. Our calculations clearly show thatsolvation effects strongly influence cation selectivity.1,3-diethoxy-p-tert-butylcalix-[4]crown-5isomers preferentially bind Na~+, not K~+as found in aqueous environments.However, the calculated results indicate that K~+selectivity is recovered when even afew waters of hydration are considered.Secondly, theoretical studies of a new ion-pair receptor meso-octamethylcalix[4]pyrrole (OMCP) and its interactions with the halide anions (F~-, Cl~-, and Br~-) andcesium halides (CsF, CsCl, and CsBr) have been performed. Geometries, bindingenergies, and binding enthalpies are evaluated at the restricted hybrid Becke’sthree-parameter exchange functional (B3LYP) method using6-31+G(d) basis set andrelativistic effective core potentials. The optimized geometric structures are used toperform natural bond orbital (NBO) analysis. The results indicate that hydrogenbonding interactions are dominant and the halide anions (F~-, Cl~-, and Br~-) offer lone pair electrons to the contacting σ*(N–H) or σ*(C–H) antibond orbitals of OMCP. Inaddition, electrostatic interactions between lone pair electrons of halide anion and theLP*orbitals of Cs+, and the cation–π interactions between the metal ion and π-orbitalsof pyrrole rings play a certain role in the Cs~+·OMCP·X~-complexes. The currentstudies further demonstrate that the easy-to-make OMCP host compound not onlyfunction as anion receptor but can act as ion-pair receptor.Thirdly, a novel fluorescent switchable chemosensor1, which is composed of aanthracene-modified calix[4]crown in the1,3-alternate conformation, was calculatedby density functional theory (DFT) and time-dependent density functional theory(TDDFT) method. Geometries, molecular orbitals (MOs) and binding thermalenergies were evaluated at the restricted hybrid Becke’s three-parameter exchangefunctional (B3LYP) using6-31G(d) basis set and relativistic effective core potentials(LanL2DZ). The calculations indicate that because of the photoinduced electrontransfer (PET) effect, the addition of alkali metal ions have hardly any effect on thefluorescence of ligand1under neutral or basic conditions. Also, the high selectivity ofligand1for K~+and Rb~+, under acidic conditions, the complexed metal ion can resultin ammonium ion deprotonation, which leads to quenching of fluorescence of1H+.Theoretical studies of a diquinone calix[4]arene and its interactions with thecations Li~+, Na~+, K~+, and Ag~+have been performed. Conformational features andcation-binding properties were evaluated with the restricted hybrid Beckethree-parameter exchange functional (B3LYP) method using the6-31G(d) basis setand relativistic effective core potentials. To model the effect of medium, thepolarizable continuum model (PCM) was also employed. The calculated results showthat the most stable conformers are1,3-alternate and partial cone in the gas phase andin CH2Cl2solution, respectively. The optimized geometric structures were used toperform natural bond orbital (NBO) analysis. The two main types of driving forcemetal-ligand and cation-π interactions are investigated. The calculated binding energyfor cations (Li~+, Na~+, K~+, and Ag~+) are discussed. The calculated results indicate thatcone complexes are the most stable.