A Study on the structure and reactivity of encounter complex

在溶液中的化学反应中，人们认为某些聚吡啶混配配体的三配位金属络合物是完全球形的。然而，从混配Ru(II)络合物到Cr(III)络合物的能量传递速率常数的实验结果表明，在水溶液中，能量供体混配络合物周围不存在能量受体络合物。换言之，即使在溶液中遇到络合物，混配的Ru(II)-络合物和Cr(III)络合物之间的相对几何构型也不是各向同性的，而是各向异性的。在水-乙醇-水的混合溶剂中，供体配体与受体配体之间的亲和性对络合物的疏水性、亲水性等结构有着重要的影响。8：2和6：4)，相遇络合物的相对几何构型与水溶液不同。这些结果表明，乙醇和乙腈的溶剂分子对偶遇络合物的相对几何构型有影响。因此，金属-络合物之间光激发能量转移速率常数的测定使得溶液中偶遇络合物的结构成为可能。本工作的结果具有非常广泛的应用，特别是在活体化学反应领域。

It has been thought that the tris-chelate metal-complexes of mixed-ligands of some poly-pyridines are completely spherical in chemical reaction in solution. However, the experimental results of energy-transfer rate-constant from the mixed-ligand Ru(II)-complex to Cr(III) complex indicate that the energy-acceptor complexes do not exist around the mixed-ligands complexes of energy-donor in encounter complex in aqueous solution. In other words, the relative geometry between the mixed-ligand Ru(II)-complex and Cr(III) complex are not isotropic but anisotropic even in encounter complex in solution. The congeniality between donor's ligand and acceptor's ligand is very important for the structure of encounter complex in aqueous solution, for example, hydrophobicity and hydrophilicity.In mixed-solvents of water : ethanol and water : acetonitrile (v.v. 8 : 2 and 6 : 4), the relative geometry of encounter complex is different from that in aqueous solution. These results indicate that the solvent molecules of ethanol and acetonitrile affect on the relative geometry of encounter complex.Therefore, the determination of the rate-constant of photo-excitaion energy-transfer between metal-complexes makes it possible for the structure of encounter complex in solution as molecular level.The results in this work have a very wide application, especially in the region of chemical reaction in a living body.