Influence of position of methoxy groups in Zn-methoxyphenylporphyrins

Abstract

The crystal structure of the compound, Zn(II) 5,10,15,20-tetrakis(meta-methoxyphenyl)porphyrin chloroform trisolvate, $$[\hbox {ZnT}(m\hbox {-OCH}_{3})\hbox {PP}]{\cdot } 3\hbox {CHCl}_{3}$$ 1 reveals that it forms a weak one-dimensional chain structure through interaction between Zn of porphyrin and the oxygen atom of the methoxy group of a neighbouring porphyrin. The zinc–oxygen interaction observed in compound 1 is compared with Zn(II) 5,10,15,20-tetrakis(para-methoxyphenyl)porphyrin $$[\hbox {ZnT}(p\hbox {-OCH}_{3})\hbox {PP}]$$ 2 and Zn(II) 5,10,15,20-tetrakis(3,4,5-tri-methoxyphenyl)porphyrin $$[\hbox {ZnT}(3,4,5\hbox {-triOCH}_{3})\hbox {PP}]$$ 3 to understand the preferred methoxy-position of interaction. The strength of the non-covalent zinc–oxygen (methoxy group of a neighboring porphyrin) interaction in compound 1 is in between that of similar interactions observed in compounds 2 and 3. The Mulliken charge analysis using theoretical calculation at the DFT level shows that the meta-methoxy oxygen has a higher probability of binding to the metal than the para-methoxy oxygen. In the presence of nucleophiles, the formation of one-dimensional chain structure stops due to the binding of the nucleophiles to the metal zinc. The photoluminescence and differential scanning calorimetric studies were also performed for compound 1. SYNOPSIS A zinc porphyrin $$[\hbox {ZnT}(m\hbox {-OCH}_{3})\hbox {PP}]{\cdot } 3\hbox {CHCl}_{3}$$ 1 has been synthesized and structurally characterized using single crystal X-ray diffraction and other spectroscopic methods. The crystal structure of 1 shows a weak interaction between Zn of porphyrin and the oxygen atom of the methoxy group of a neighbouring porphyrin. The Zn-oxygen interaction observed in compound 1 is compared with Zn-oxygen interaction present in other methoxy-substituted porphyrins $$[\hbox {ZnT}(p\hbox {-OCH}_{3})\hbox {PP}]$$ 2 and [ZnT(3,4, 5- $$\hbox {triOCH}_{3})\hbox {PP}$$ ] 3.