Thermal splitting of Bis-Cu(II) octaphyrin(1.1.1.1.1.1.1.1) into two Cu(II) porphyrins

When heated, bis-Cu(II) octaphyrin(1.1.1.1.1.1.1.1) is quantitatively split into two Cu(II) porphyrins both in solution and film states, which is accompanied by large absorption spectral changes.     

Meso-substituted [34]octaphyrin(1.1.1.0.1.1.1.0) and corrole formation in reactions of a dipyrromethanedicarbinol with 2,2'-bipyrrole

The reaction of a dipyrromethanedicarbinol with 2,2'-bipyrrole leading to meso-substituted [34]octaphyrin(1.1.1.0.1.1.1.0) and/or corrole was investigated to determine the effect of key reaction parameters on the distribution of the two macrocycles. Solvent, acid catalyst, acid quantity, oxidant, oxidant quantity, and reaction time were surveyed for a model reaction affording 5,10,19,24,29,38-hexaphenyl[34]octaphyrin(1.1.1.0.1.1.1.0) (HPO) and/or meso-triphenylcorrole (TPC). HPO was found to be a fairly ubiquitous product, produced in yields as high as 23% (UV-vis), while TPC was observed infrequently, in yields up to 10% (UV-vis). A preparative-scale reaction provided HPO in an isolated yield of 25%. The methodology was extended to the synthesis of an octaphyrin bearing two different substituents in defined locations and to an octaphyrin possessing electron-withdrawing pentafluorophenyl substituents. Preferential formation of octaphyrin instead of corrole suggests that the anti conformation of 2,2'-bipyrrole is the relevant form under the reaction conditions surveyed. The spectral properties of the novel meso-substituted [34]octaphyrin(1.1.1.0.1.1.1.0) species are similar to those of the known beta-substituted analogue, including spectra consistent with the absence of macrocycle aromaticity despite a main conjugation path of 34 pi-electrons. Key to the overall study was the development of a refined synthesis of 2,2'-bipyrrole.     

Effect of carbinol group placement on complementary reactions of dipyrromethane+bipyrrole species leading to corrole and/or an octaphyrin

Complementary reactions of a dipyrromethanedicarbinol+2,2′-bipyrrole and a 2,2′-bipyrroledicarbinol+a dipyrromethane were investigated to determine the effect of carbinol group placement on the product distribution and on the broader reaction course. Analytical-scale reactions were performed for both reactions to explore the interplay of acid catalyst, acid concentration, and solvent on the yield of corrole and an octaphyrin. The two reaction routes were further compared under representative conditions by assessing acid-catalyzed decomposition of the dicarbinol species affording benzaldehyde (TLC and GC-MS) and by performing time course experiments monitoring macrocycle yield (UV-vis), presence of benzaldehyde (TLC), and oligomer composition (LD-MS). The complementary reactions were generally found to be quite different. Key to this work was the refinement of a method for the acylation of 2,2′-bipyrrole.     

Geometrical structure and nonlinear response variations of metal (M = Ni2+, Pd2+, Pt2+) octaphyrin complex derivatives: A DFT study

Nonlinear optical response of designed organometallic complexes of Ni²⁺, Pd²⁺, and Pt²⁺ metal ions with octaphyrin (OP) as ligand were explored by using DFT at CAM-B3LYP/6–311G++(d, p)/LANL2DZ/DEF2SV level of theory. The geometries of these organometallic complexes were studied in terms of effect on molecular framework by metal ion and substituent groups. The optimized geometry of free ligand displays that one of the four pyrrole rings orients out of plane to reduce the steric hindrance. The effect of the substituents on the geometry was found more prominent in the Ni²⁺-OP complexes. The calculations reveal enhancement in the values of dipole moment and hyperpolarizability on introducing electron withdrawing and electron donating groups in ligand framework with maximum enhancement in case of Pt²⁺-OP derivatives. In this study no regular trend was observed for the HOMO and LUMO energies with the second-order hyperpolarizability of M²⁺-OP complexes. However, we have observed that the excited-state properties calculated by using TD-DFT correlate well with the second-order hyperpolarizability values and the dependence was rationalized in terms of two-level model. Thus, from overall calculations we have observed that the designed organometallic complexes display higher polarizability and hyperpolarizability values and can be effective candidates for nonlinear response.