DFT Study On Electronic Structures And Proton Transfer For Complexes Of2-substituted Benzazole Derivatives With Alkali(Earth) Metal Ions

As one of the basic chemical or biochemical reactions, proton transfer reactionsexist in a variety of chemical and biochemical processes. In the system of life, as thetrace elements, K+, Na+, Ca2+and other alkali/earth metal cations Mn+have a veryunusual significant role. For example, potassium is one of the important elementsneeded by the body charging with the maintenance of osmotic pressure within thecells of the human body and maintaining the normal excitatory neuromuscularfunctions, the metal ions Mn+can interfere with replication of RNA or DNA synthesisand dissociation process. With theoretical calculations, the paper focuses on theinteractions of2-substituted benzoimiazole derivatives with alkali/earth metal ionsand its impact on proton transfer of the complexes. The main results were as follows:1、 Theoretical investigation on the interactions and intramolecular protontransfer of cation-π-complexes of2-(2-Hydroxyphenyl) benzoimidazole with Na+, K+,Ca2+and other alkali/earth metal ions at B3LYP/6-311++G (d,p) level by usingdensity functional theory. The results showed that the cation-π interactions were verystrong. Series of calculated results, such as the twist angle T of cation-π-complexesaromatic ring, distorted energy ET, interaction energy, total bond order and change ofmetal ions Mn+, electron density topological analysis intra molecular hydrogen bondcritical point, the relative energy, NMR and those results showed that the alkali/earthmetal ions Mn+and solvent effect can change the energy barrier of the HBIintramolecular proton transfer process. It was closely related with the strength ofhydrogen bond, the more stronger of the bond, the more easiler for proton transfer.The influence of M2+is higher than M+ion. The addition of Mn+can promote orhinder the proton transfer, it could also make advantage structural reverse, canregulate the course of the transfer to HBI.2、The features of2-(3-sulfhydryl-2-pyridyl)benzothiazole (MPyBT) with Mn+and its proton transfer were investigated theoretically at the B3LYP/6-311++G(d,p)level. Molecular electrostatic potential can tell us that the alkali metal ions formcomplexes with double or single teeth. At the same time, stable complexes wereobtained by optimizing initial geometrical structure. The data of composite property relative energy, binding energy, properties of hydrogen bond saddle point in cation-πcomplexes analysis by using the atoms in molecules theory (AIM), calculation ofNMR chemical shift of the proton transfer and those indicated that the addition ofalkali/earth metal ion Mn+or adjusting the coordination range can cause variation ofhydrogen bond in MPyBT molecules, and ions M2+have more influence than thealkali metal ions M+, which can weaken the intramolecular hydrogen bond of MPyBT.3、The intramolecular proton transfer of cation-π-complexes of2-(3-hydroxyl-2-pyridyl)benzoimidazole(HPyBI) with alkali/earth metal ions Mn+were studied atB3LYP/6-311++G(d,p) level. The results showed that there is a the cation-πinteraction in these complexes. The twist angle T of cation-π-complexes aromatic ring,distorted energy ET, interaction energy, total bond order and change of metal ionsMn+, electron density topological analysis intra molecular hydrogen bond criticalpoint (AIM), the relative energy and magnetic calculation showed that the alkali/earthmetal ions and solvent effect can change the energy barrier of HBI intramolecularproton transfer(IPT) process. The IPT is together with its bonding strength, the morestronger, the more easiler. The influence of M2+is more higher than M+ion, what ismore, the addition of Mn+can facilitate or impede the transfer process of H proton,which regulates the proton transfer of HPyBI.4、 The proton transfer of cation-π-complexes of2-(2-sulfhydryl phenyl)benzoimidazole(MBI) with Mn+(Na+, K+, Ca2+, et al) were by using B3LYP/6-311++G(d, p) theoretical methods. It was show that the cation-π interactions werevery strong and the metal ions or solvent effect can change energy barrier of the IPTthrought the calculated results about the twist angle T of cation-π-complexes aromaticring, distorted energy ET, interaction energy, total bond order, metal ions charge,electron density topological intra molecular hydrogen bond critical point, relativeenergy and NMR. The impact of M2+is more higher than M+ions, metal ion Mn+joining can facilitate or impede its proton transfer and advantages of structuralreverse, then Mn+-MBI proton transfer process can be controlled.