Premium
The π Complexation of Alkali and Alkaline Earth Ions by the Use of meso ‐Octaalkylporphyrinogen and Aromatic Hydrocarbons
Author(s) -
Bonomo Lucia,
Solari Euro,
Scopelliti Rosario,
Floriani Carlo
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20010316)7:6<1322::aid-chem1322>3.0.co;2-h
Subject(s) - chemistry , alkali metal , polymerization , monomer , crystallography , ion , polymer , photochemistry , organic chemistry
The full metallation of meso‐ octaalkylporphyrinogens [R 8 N 4 H 4 ] (R=Et, 1 ; n Bu, 2 ; CH 2 Ph, 3 ; (CH 2 ) 4 , 4 ) with heavy alkali metals (M=K, Rb, Cs) leads to the porphyrinogen‐M 4 compounds, in which the solvation of the alkali cations is largely assured by the intra‐ and intermolecular π‐interactions with the pyrrolyl anions. Such a mode of complexation results in a structural diversity as a function of the meso substituents, the size of the metal ion, and the solvent. The structure of the unsolvated polymers [R 8 N 4 M 4 ] n (R=Et, M=K, 5 ; M=Rb, 6 ; M=Cs, 7 ; R=(CH 2 ) 4 , M=Rb, 8 ; M=Cs, 9 ) have been clarified through the X‐ray analysis of 7 recrystallized from diglyme. The structure shows that the tetraanion binds two Cs ions inside the cavity, which display in one case η 1 : η 1 : η 1 : η 1 and in the other η 5 : η 5 : η 5 : η 5 interaction modes. Bidimensional polymerization is assured by four Cs ions, which each bind at the η 5 position on the exo face of each pyrrole. With bulkier meso substituents, different polymeric forms are obtained (R= n Bu, M=K, 10 ; M=Rb, 11 ; M=Cs, 12 ), and their structures were clarified through the X‐ray analysis of 10 , which was recrystallized from dimethoxyethane. The polymeric units are made up by the monomeric units [Bu 8 N 4 K 2 ] 2− , in which one potassium is η 1 : η 1 : η 1 : η 5 and the other η 5 : η 1 : η 5 : η 1 bonded inside the porphyrinogen cavity. In the case of R=CH 2 Ph, the monomeric anion [(PhCH 2 ) 8 N 4 K 2 ] 2− ( 13 ) has been structurally identified. The metallation of 1 and 2 with active forms of alkaline earth metals (M′=Ca, Sr, Ba) led to dinuclear compounds [R 8 N 4 M′ 2 ] (R=Et, M′=Ca, 14 ; M′=Sr, 15 ; M′=Ba, 16 ; R= n Bu. M′=Ba, 18 ), in which both metals inside the cavity are η 1 : η 3 : η 1 : η 3 (Ca) and η 1 : η 5 : η 1 : η 5 (Sr and Ba) bonded to the porphyrinogen tetraanion. The coordination sphere of each metal ion is completed by two THF molecules, which, in the case of Ba, are easily replaced by an arene ring [Bu 8 N 4 Ba 2 ( η 6 ‐arene) 2 ] (arene=durene, 22 ; naphthalene, 23 ; toluene, 24 ; benzene, 25 ). The X‐ray structures of 14, 15, 18, 22 , and 23 are described in detail. We have tried to establish a relationship between the solid‐state and solution structures by analyzing the 1 H NMR spectra of the porphyrinogen complexes.