Substituent Effect on Porphyrin Ring Distortion

以吡咯、二苯基吡咯和2，6-二氟二氯苯甲醛为原料，通过混合缩合反应合成了一系列具有中-(2，6-二氟或二氯苯基)取代基的卟啉化合物。本文报道的卟啉化合物简写如下：四芳基卟啉(TXPP)、六芳基卟啉(HXPP)、反式辛基卟啉(Trans-OXPP)、顺式辛基卟啉(cis-OXPP)、十芳基卟啉(DecxPP)和十二芳基卟啉(DXPP)，其中X=F或Cl.苯基取代基的增加对紫外可见光谱有较大影响，Soret谱带按TXPP&lt；HXPP&lt；反式-OXPP、顺式-OXPP&lt；DecxPP&lt；DXPP；DXPP的顺序逐渐红移.然而，X=F系列和X=Cl系列的红移幅度不同。人们很容易认为X=F Seris和X=ClSeris的卟啉环扭曲程度是不同的。可能是孤对氟原子与卟啉π轨道的相互作用降低了卟啉环的扭曲，从这些卟啉的酸碱性质推测，卟啉环与中位苯环之间的共轭作用对卟啉环的扭曲有影响。此外，从酸碱滴定实验中观察到TXPP(X=F和X=Cl)在酸单离子状态下的异常稳定性。

A series of porphyrin with meso-(2,6-difluoro- or dichlorophenyl) substituents has been synthesized by mixed condensation of pyrrole, diphenylpyrrole, and 2,6-difluoro- or 2,6-dichlorobenzaldehyde. The porphyrins reported here are abbreviated as follows: tetraaryl-lporphrins (TXPP), hexaarylporphyrins (HXPP), trans-octarylporphyrins (trans-OXPP), cis-octarylporphyrins (cis-OXPP), decaarylporphyrins (DecXPP), and dodecaarylporphyrins (DXPP), where X=F or Cl.Increase of the phenyl substituents have large effect on the UV-visible spectra, gradually red-shifting the Soret bands in the order of TXPP<HXPP<trans-OXPP,cis-OXPP<DecXPP<DXPP. However, the magnitude of the red shift is different between X=F series and X=Cl series. It is tempting to suppose that the magnitude of porphyrin ring distortion is different between X=F seris and X=Cl seris. It is possible that interaction between lone pair of fluorin atoms and porphyrin π orbitals reduce the porphyrin ring distortion.From the acid-base properties of these porphyrins, it is supposed that conjugation between porphyrin ring and meso-phenyl ring has influence upon the porphyrin ring distortion. Furthermore, an unusual stability in the acid monocation state of TXPP (X=F and X=Cl) is observed from the acid-base titration experiments.