No abstract

One-pot facile synthesis and characterization of novel β-substituted meso-tetraphenylporphyrins and/or chlorins were described. The high regioselective reactivity of active methylene compounds in Michael addition reaction was reported to access β-substituted trans-chlorins. Size-dependent approach was applied for the fine-tuning of product formation from porphyrins to chlorins. Notably, we were able to isolate mono/trisubstituted porphyrin and/or di/tetra-substituted chlorin from one-pot synthesis for the first time in porphyrin chemistry. Single-crystal X-ray diffraction analysis revealed the quasiplanar to moderate nonplanar conformation of chlorins due to trans orientation of β-substituents, whereas porphyrins exhibited higher mean plane deviation from 24-atom core (Δ24) as compared to chlorins. β-Functionalized chlorins exhibited lower protonation constants and much higher deprotonation constants as compared to porphyrins revealing the combined effect of the conformation of macrocyclic core and the electronic nature of β-substituents. Facile synthesis of porphyrins and/or chlorins based on the size of Michael donor employed and in turn resulted in tunable photophysical and electrochemical redox properties are the significant features of the present work.

It is well‐known that treatment of β‐octaethylporphyrin with H2O2/conc. H2SO4 converts it to a β‐oxochlorin as well as all five constitutional isomers of the corresponding β,β’‐dioxo‐derivatives: two bacteriochlorin‐type isomers (β‐oxo groups at opposite pyrrolic building blocks) and three isobacteriochlorin‐type isomers (β‐oxo‐groups at adjacent pyrrolic building blocks). By virtue of the presence of the strongly electronically coupled β‐oxo auxochromes, none of the chromophores are archetypical chlorins, bacteriochlorins, or isobacteriochlorins. Here the authors present, inter alia, the single crystal X‐ray structures of all free‐base diketone isomers and a comparative description of their UV‐vis absorption spectra in neutral and acidic solutions, and fluorescence emission and singlet oxygen photosensitization properties, Magnetic Circular Dichroism (MCD) spectra, and singlet excited state lifetimes. DFT computations uncover underlying tautomeric equilibria and electronic interactions controlling their electronic properties, adding to the understanding of porphyrinoids carrying β‐oxo functionalities. This comparative study lays the basis for their further study and utilization.

The four possible pyrrocorphin isomers were prepared. Remarkably, they show regiochemically dependent aromaticity attributed to the presence of a 16-membered, 18 π-electron aromatic ring-current.

Highly nonplanar electron deficient perhaloporphyrins were utilized for the detection of basic anions such as CN−, F−, CH3COO−and H2PO4−viaanion induced deprotonation. These sensors can be reusable without loss of their sensing ability.