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5,15-substituted porphyrins are valuable compounds in bioorganic and materials chemistry. A new synthesis has been developed that employs 1,9-diformylation of a dipyrromethane, conversion of the diformyldipyrromethane to the bis(imino) derivative, and reaction of the bis(imino)dipyrromethane + a dipyrromethane to give the zinc-porphyrin bearing trans-AB-substituents. 1,9-diformylation was achieved via Vilsmeier reaction. Imination was achieved by treatment of the 1,9-diformyldipyrromethane with excess amine under neat conditions at room temperature. The porphyrin-forming reaction was carried out over 2 h in refluxing ethanol containing zinc acetate exposed to air. Oxidation of the intermediate porphyrinogen occurs aerobically. A complex composed of two bis(imino)dipyrromethanes and two zinc atoms was observed to form reversibly during the course of the reaction. A set of zinc-porphyrins with trans-AB-, A₂-, or A-substituents has been prepared in yields of ~30% (without detectable scrambling) with straightforward purification. The reaction is applicable to A/B substituent combinations of aryl/aryl, aryl/alkyl, and aryl/H.

Dipyrrins are valuable precursors to dyes [dipyrrinatoboron difluoride, bis(dipyrrinato)-zinc(II) complexes] and serve as ligands in a variety of self-assembled materials. Six new dipyrrin-containing architectures have been synthesized. The architectures include bis(dipyrrinato) complexes containing copper(II) or palladium(II), a dipyrrin bearing a protected phosphonic acid unit, a porphyrin bearing two dipyrrins in a trans configuration, a linear diphenylethyne-linked dipyrromethane-dipyrrin building block, and a triad composed of two zinc porphyrins joined via an intervening bis(dipyrrinato)copper(II) complex. Two porphodimethenatozinc complexes were prepared and found to have Φ_f ≤ 0.002 (in toluene at room temperature), which is substantially less than the analogous bis(dipyrrinato)zinc complexes. Taken together, the syntheses described herein should broaden access to dipyrrins for use as complexation motifs in supramolecular chemistry and as pigments in light-harvesting applications.

Porphyrins may serve as the active charge-storage medium in memory chips. A series of 14 porphyrins (trans-A₂B₂, trans-AB₂C, or A₄ type; free base, copper or zinc chelate) has been synthesized for investigation of metal deposition on porphyrin monolayers. Each trans-AB₂C porphyrin is equipped with a surface attachment group and a distal functional group (or flanking functional groups). The surface attachment groups include S-acetylthiomethyl, hydroxymethyl, TMS-ethynyl, allyl, and triallylmethyl; the functional groups include amino, cyano, dipyrrin-5-yl, formyl, and nitro; all of which are attached to the p-position of a porphyrin meso-phenyl group. Two non-redox-active triallylmethyl-substituted arenes were also prepared for use as control compounds.

The Thompson group aims to further the chemistry of pyrroles, dipyrrins and prodigiosenes. This micro-review discusses each of these research areas in turn, focussing on our achievements thus far.

A tetrapyrrolic macrocycle containing ethenylene and dioxyphenylene bridges was obtained through the reaction of a dipyrrin-DDQ adduct with triethylamine. The structure of the macrocycle was elucidated by X-ray diffraction analysis. The macrocycle exhibited solvent-dependent absorption spectra due to intramolecular charge transfer interactions.

A series of meso-aryloxy linked BODIPY monomers, dimers and trimer were synthesized by nucleophilic aromatic substitution (S_NAr) reaction from phenols with meso-chloro BODIPY and their photophysical properties were systematically studied by UV-vis and fluorescence spectroscopy. The relationship between their photophysical properties and the spatial arrangement of meso-aryloxy linked BODIPYs has been discussed. The monomers exhibited different extent solvent-dependent fluorescence, and fluorescence quenching in polar solvents were found relative to the HOMO energies of the donor (meso-phenols), indicating possible PET effect from meso-phenols to the BODIPY fluorophore. Ortho-dimer showed unusual broad red-shifted emission bands centered at 550 nm with a larger Stokes shifts at the range of 2900–3400 cm${}^{-1}$, and low fluorescence quantum yields, which was in sharp contrast to those of other dimers and trimer, indicating of possible excimeric species formation due to slipped cofacial arrangement ofortho-dimer.

Three new covalently linked BODIPY-metal dipyrrin conjugates (Pd${}^{2+}$, Zn${}^{2+}$ and Re${}^{1+})$ were synthesized by treating $\beta$-dipyrrinyl BODIPY with appropriate metal salts in toluene in the presence of triethylamine at 120$deg$ C. The conjugates were isolated in decent yields either by recrystallization or by column chromatographic purification. The conjugates were thoroughly characterized by 1D and 2D NMR spectroscopy, absorption, cyclic voltammetry and DFT/TD-DFT studies. The studies revealed that the BODIPY and metal dipyrrin moieties in conjugates interact very weakly with each other and retain their individual characteristic features. The conjugates are electron deficient and non-fluorescent in nature.

While dipyrrin-boron complexes (BODIPYs) and their derivatives have attracted much attention, dipyrrin-based metal complexes recently appeared as a novel luminescent material. So far, dipyrrin-metal complexes have been regarded as non-luminescent or weakly luminescent. Interestingly, introduction of steric hindrance at the meso-position and the development of heteroleptic complexes with proper frontier orbital ordering are two recent strategies that have been developed to improve their luminescent ability. Compared with BODIPYs, one of the distinctive advantages of dipyrrin-metal complexes is that they can form a series of self-assembled supramolecules and polymer assemblies via facile coordination reactions. In recent times, several supramolecular, coordination polymers and Metal-Organic Frameworks (MOFs) have been developed, $e.g.$ by spontaneous coordination reactions between dipyrrin ligands and metal ions. As a novel luminescent material, dipyrrin-metal complexes have been applied in many fields. This review article summarizes recent developments in dipyrrin-metal complexes from the viewpoint of the improvement of luminescent ability, the formation of supramolecular and coordination polymers and their potential applications.

A ring-opening of nickel 10,20-dimesityl-5,15-dioxaporphyrin (NiDOP) proceeded in a reaction with aryl Grignard reagents to afford 1,9-diaryldipyrrins instead of demetallation reaction to form a free base form. A reagent scope for the ring-opening reaction revealed that reactions with less-sterically hindered aryl Grignard reagents, such as phenyl and para-substituted phenylmagnesium bromides, provided the dipyrrin products. In contrast, no reaction occurred, and unreacted NiDOP was recovered when alkyl, ethynyl, and 2-thienylmagnesium bromides and sterically hindered mesitylmagnesium bromide were used for the reactions. Herein, the unique ring-opening reactivity of NiDOP and characterization of the 1,9-diaryldipyrrin products are reported.