Theoretical Study On Nuclear Magnetic Resonance Spectra Of Metallorganic Compounds

Metallorganic compounds have become one of fascinating areas of researches in recent years. In the paper, a series of metallorganic compounds have been studied by the quantum-chemical calculation with proper basis sets, including:1. a series of carbonyl complexes.2. dibenzene chromium and its derivatives3. ferrocene and its derivatives4. a series of metallic complexes with acetylacetoneWe optimized the geometric configurations of a series carbonyl complexes including Ni(CO)4 Fe(CO)5, Cr(CO)6 with density functional theory B3LYP method at the different levels and confirmed the stable geometry by vibrational analyses. Then we calculated the nuclear magnetic resonance spectra with GIAO method provided by GAUSSION98 program at the different levels. The results show that it is important to choose a proper basis set to calculate the NMR spectra for the complexes of the first series of transition elements. Because the results show that the small basis set can't get good results and the big basis set can't get satisfied results either. The results show that the best set for optimizing the geometric configuration is 6-31++G(d,p) basis set and the best set for calculating NMR spectra is 6-31++G(d,p) basis set. We may optimize the geometric configurations at the B3LYP/6-31++G(d,p) level, and then calculate the NMR spectra at the B3LYP/6-31++G(d,p) level by using GIAO method. The results of calculation are essentially consistent with experimentalvalues. But when we calculate the big molecules, we may optimize the geometric configuration at the B3LYP/6-31G(d,p) level, and calculate their NMR spectra at the B3LYP/6-31++G(d,p) level by using GIAO method. The results of calculation will be fundmentally consistent with the experimental values.In addition, we calculated dibenzene chromium and its derivatives, ferroceneand its derivatives. The former had higher symmetry. We studied the substituenteffects by calculating their NMR spectra. The results show that: when we add asubstitute group on one ring of dibenzene chromium, the substitute group will affecttwo benzene rings. The effect is similar to the effect of branched alkanes, namely:the effect on neighbouring groups has transmissibility. Furthermore, the nearer theneighbouring group is, the stronger the effect is. This effect is observed not only onthe substituted ring, but also on the unsubstituted ring. On this basis, we calculatedthe ferrocene and its derivatives, and studied the effect of their substitute groups, theresults were consistent with the results of dibenzene chromium and its derivatives.Then, we calculated the NMR spectra of a series of metallic complexes withacetylacetone. We optimized the geometric configurations at theB3LYP/6-31++G(d,p) level, and GIAO method was used to calculated the NMRspectra of a series of metallic complexes with acetylacetone. The results ofcalculation were essentially consistent with the experimental values.The above-mentioned calculated results show that, the calculation of the NMR spectra of metallorganic compounds by the quantum-chemical calculation programs is feasible. At the same time, we can also discuss the transition of electrons and the effect of substitute groups. This paper will put forward some useful reference for theoretical and experimental researches.