合成了新型的1,3-二(1-二茂铁磺酰基-2-苯并咪唑)丙烷(BFBP).用红外光谱、核磁、质谱和x射线单晶衍射对其结构进行了表征.该晶体结构属正交晶系,空间群为Pnma,晶胞参数为:a=1.30079(13)nm,b=2.9627(3)nm,c=1.01257(10)nm,V=3.9023(7)nm^3,Dc=1.492g/cm^3,μ=0.907mm^-1,F(000)=1816,Z=4,R1=0.0506,wR2=0.1583.晶体结构表明,标题化合物的两个二茂铁磺酰基采取顺式连接方式,即为顺式构象而不是反式构象.运用密度泛函理论,采用B3LYP/6—31G方法,分别对标题化合物的顺式和反式构象进行几何全优化,得到两种优化结构a-BFBP(顺式优化结果)和β-BFBP(反式优化结果).两种优化结构的键长、键角计算值接近,并大多与实验值相一致,说明计算方法正确,计算结果可靠.比较两种优化结构的总能量,α-BFBP的总能量远低于β-BFBP,从热力学角度考虑,α-BFBP的稳定性远高于卢β-BFBP.比较两种优化结构的HOMO能级,α—BFBP的HOMO能级低于卢β-BFBP,说明β-BFBP的抗氧化能力强于卢β-BFBP.比较两种优化结构的前沿轨道间的能量间隙,α-BFBP的能量间隙高于卢β-BFBP,说明α-BFBP的基态稳定性更好,电子难以激发.总之,量子化学计算结果很好地佐证了实验结果.分析标题化合物采取顺式构象是由丙基锯齿链折叠端方向所决定的.
A new compound, 1,3-bis(1-ferrocenesulfonyl-2-benzimidazolyl)propane, has been prepared, and characterized by IH NMR, IR, MS and X-ray single crystal diffraction. Its crystal structure belongs to orthorhombic system, space group Pnma, with a= 1.30079(13) nm, b=2.9627(3) nm, c= 1.01257(10) nm, V= 3.9023(7) nm^3, Dr= 1.492 g/cm^3,/a=0.907 mm-1, Z=4, F(000)= 1816, RI =0.0506, wR2=0.1583. The crystal structure shows that the title compound is cis-configurafion, and not trans-configurafion. The cis-configuration and the trans-configuration of the title compound are fully optimized by B3LYP/6-31G method in Gaussian 03 package, and the optimized structures in theory are α-BFBP (cis-configuration) and β-BFBP (trans-configuration), respectively. The results show that the bond lengths and bond angles obtainedby quantum chemical calculation are almost the same with those of the experiment, suggesting that the molecular geometry optimization of the structures are reliable and the calculation method used is reliable. Es- pecially, α-BFBP is in accordance with the crystal structure in the main. The molecular total energy of α-BFBP is far lower than that of β-BFBP, indicating that the cis-configuration of the title compound is more stable than the trans-configuration from the thermodynamic point of view. The HOMO energy of α-BFBP is lower than that of β-BFBP, suggesting that antioxidative potential of α-BFBP is superior than β-BFBP. The energy gap of frontier molecular orbits of α-BFBP is bigger than that of βl-BFBP, indicating that the ground state of α-BFBP has better stability. In a word, the quantum chemical calculation of the title compound provides a good testimony for the crystal structure. The cis-configuration of the title compound is attributed to terminal direction of zigzag propyl between two benzimidazolyl.