Theoretical Study On Chemiluminescence Reagent Of Phthalhydrazide

Phthalhydrazide derivatives are a class of sensitive chemiluminescence reagent, and they have been widely used in the antivirus, antitumor, antimalaria, insecticide, sterilization, etc. To further enhance the sensitivity and widen the application range of this method, the design and synthesis of new phthalhydrazide derivatives with high chemiluminescence quantum yield have attracted a lot of attention. In this paper, the theory calculation method was used to study phthalhydrazide derivatives properties between structure and electronic spectra, aiming to be found some molecules with good luminescence properties, and further broaden the application range of this kind of compounds.This paper mainly used the theoretical calculation methods to investigate the structure and frontier molecular orbital of the phthalhydrazide derivatives. The specific research contents are as follows:1. Phthalhydrazide compounds including luminol,7-amino-6-sulfanylphthalazine-1, 4(2 H, 3 H)-dione(ASPH) and its derivatives were investigated using quantum chemical calculation method. The main purpose was searching for the relationshipbetween a certain parameter and chemiluminescence properties,which can provide help for the design of chemiluminescence analogues with high quantum yields. By discussing the bond length,dihedral angle, frontier molecular orbital and orbital energy values, a linear correlation was observed between HOMO-LUMO energy gaps((35) Egap) and their relative chemiluminescence intensity. Based on these, a series of ASPH derivatives were simulated and some of the molecules were considered as promising excellent chemiluminescence reagent.2. Density functional theory at the B3LYP/6-311G(d, p) level was used to obtain the optimised geometries of a series of2-(1 ?-pyrenyl)phthalazino[6, 7-d]thiazole-5, 8(6H, 7H)-dione–water complexes with stoichiometric ratios ranging from 1:1 to 1:5 both in the gas phase and in aqueous solution. All the calculations show that there are strong hydrogen bond interactions between luminol and water due to the existence of C=O and N-H groups in2-(1?-pyrenyl)phthalazino[6, 7-d]thiazole-5, 8(6H, 7H)-dione molecule.By comparing the relative energy and binding energy, the most stable hydrogen bond complex is suggested, which involves extended hydrogen-bonding networks. Then the changes of compound geometry structure, charge distribution and frontier orbital properties induced by hydrogen bond were investigated. The results show that the hydrogen bonds increase the planarity of system. This work will be helpful for understanding the effect of hydrogen bond on hydrazide chemiluminescence reagents.3. Phthalhydrazide derivatives are a kind of strong chemiluminescence reagent. Despite its practical importance, thisfamily of compounds has been poorly characterized from a physico-chemical point of view. For instance, their pKa values have not been reported earlier in computational chemistry. In this paper,the pKavalues of some phthalhydrazide derivatives were calculated using ab initio and two density functional methods with 6-311++G(d, p)basis set and solvent effects calculated using the PCM model.Subsequently, the effect of structural modification on pKa values was analyzed. The results showed that pKa1 was influenced by structural modification as it varied between 0.25 and 6.99, and that pKa2 was relatively less variable from 16.66 to 21.11. The high values of pKa2 revealed that a strong alkaline solution was necessary for all chemiluminescent reactions of discussed phthalhydrazide derivatives. These findings are helpful to predict chemiluminescence condition of the discussed phthalhydrazide derivatives.