Study On Design，Synthesis And Properties Of Amines And Amides Anion Recognition Receptor

Anions play an important role in biological sciences andenvironmental chemisty. Most of the anions are good hydrogenbonding receptors. Design and synthesis of new anion recognitionreceptors have become more and more interesting. Improvingselectivity and sensitivity of anion recognition should be the keyfactors to consider in the design process. So far, the designing ofnew anion receptor is still a challenging job. Hydrogen bonding isone of the interactions in anion recognition. The anion receptorscontaining N—H groups, for example, polyamines, ureas, pyrazolesand amides etc, have been paid much attention and have beenwidely used in the design of the anion recognition receptors andsensors.In order to further understanding the hydrogen bondinginteraction between N—H groups and anions, this paper designed aseries of amine and amides as prototypes of hydrogen donor inhydrogen-bond complex. The geometry optimizations (acceptormolecule and hydrogen bonding complexes) were performed, usingB3LYP/aug-cc-pVDZ method. According to the calculation results,the strength of hydrogen bonding, the charge transfer (between accepter and the doner) and harmonic frequency were investigated.Based on the TD/B3LYP/aug-cc-pVDZ level, we got the absorptionspectra of these complexes. The hydrogen bonding interactioncaused a red shift in the absorption spectra.Main content summed up as follows:(a). We optimized the geometries of the complexes of Cl-withthe amines and amides. All of receptor molecules and Cl-werehelded together by hydrogen bonding. In all hydrogen bondingcomplexes, N—H bond lengths were slightly increased.(b). The substituents can change the acidity of N—H group inamines and amides. Introducing some strong pull electronic group(-NO2), the hydrogen bond between host and anion was graduallystrengthened. And N—H acidity of the molecules in the host wasincreased, and this is helpful to complex formation.(c). Based on NBO analysis, the stabilization energy of thecomplexes was determined by the maximum value of theΔΕ2caused by the electron transition of the n(4)Cl/σ*(N—H). The N—H…Cl-hydrogen bonds between the Cl-and amines ( amides) moleculespresent a charge transfer from the lone pairs of the proton acceptorto the antibonding orbitals of N—H bonds. At the same time, theamount of charge transfer were significant different. In addition,NBO analysis indicates that a stronger hydrogen bond in N—H…Cl-results in more charge transfer between the hydrogen bond donorand acceptor molecules. The more charge transfer was, the morestable complexes were.(d). Using the TD/B3LYP/aug-cc-pVDZ, we calculated theabsorption spectra. As shown by the calculated, a large shift of the maximum absorption wavelengths. The formation of hydrogenbonds promoted the infamolecular charge transfer, and increasedrigidity of the structure. Introducing strong pull electronic groups,the red shift phenomenon became more obvious.