Synthesis of Unique Extended π Structures by Pt-Mediated Benzannulation of Nickel(II) Tetraalkynylporphyrins

Unravelling a trichloroacetic acid-catalyzed cascade access to benzo[f]chromeno[2,3-h]quinoxalinoporphyrins

A facile one-pot four-component synthetic methodology is evolved to construct novel copper(II) benzo[f]chromeno[2,3-h]quinoxalinoporphyrins in good yields via a sequential reaction of copper(II) 2,3-diamino-5,10,15,20-tetraarylporphyrins, 2-hydroxynaphthalene-1,4-dione, aromatic aldehydes, and dimedone in the presence of a catalytic amount of trichloroacetic acid in chloroform at 65 °C. Further, the newly prepared copper(II) porphyrins were transformed to the corresponding free base and zinc(II) benzo[f]chromeno[2,3-h]quinoxalinoporphyrins under standard demetallation and zinc insertion conditions. The absorption and emission properties of the obtained porphyrins were investigated by using UV-visible and fluorescence spectroscopy. The preliminary photophysical results revealed a significant red-shift in their absorption and emission spectra as compared to the meso-tetrakis(4-methylphenyl)porphyrins due to the extended π-conjugation.

Construction of coumarin-fused pyrido[2,3-b]porphyrins through a trichloroacetic acid-accelerated domino approach

A one-pot strategy for coumarin-fused Ni(ii) and Cu(ii) pyrido[2,3-b]porphyrins is developed. These porphyrinoids displayed a significant red-shift in their UV-Vis spectra.

The Outliers: Metal-Mediated Radical Reagents for Biological Substrate Degradation

The predictable and controllable interaction of small organic or peptidic molecules with biological substrates is the primary reason most pharmaceuticals are narrowly decorated carbon frameworks. The inhibition or activation binding models are measurable and without side reactions that can cause pathological angst. Yet many diseases, especially those involving rapid proliferation of cells (i.e., cancer) or aggregation of peptides (e.g., heart disease, Alzheimer's disease) have not yet been cured by inhibition therapeutics. Additionally, interventional medicine is often required to alleviate such maladies by physical removal first, followed by molecular-level therapy as a second stage. Thus, there appears to be a niche for more aggressive therapeutics that may employ harsher chemical processes to realize clinical efficacy, albeit without causing catastrophic side effects. Molecules that may be considered for this challenge are not typically biomimetic, nor do they fit the traditional pharmaceutical paradigm. They may have unusual modes of action or undesired reactivity that can be lethal if not controlled. These are the outliers; potential pharmacophores that biology does not know how to manage or adapt to. This is why they may be an intriguing class of agents that needs continuous development. In this Account, we connect the under-developed enediyne family of compounds and our metalloenediyne derivatives to existing radical-based therapeutics such as bleomycin and doxorubicin to illustrate that controlled diradical reactivity, although an outlier mechanism, has a place in the therapeutic portfolio. This is self-evident in that of the 11 natural product enediynes known, 2 have clinical impact, a strong ratio. We expand on the chemical diversity of potential enediyne constructs and focus on the accessible trigger mechanisms to activate diradical formation as a method to control toxicity. Moreover, we further illustrate how electromagnetic fields can be employed to activate both molecular and larger nanomaterial constructs that carry highly concentrated payloads of reactive reagent. Finally, we describe how controlled diradical reactivity can reach beyond traditional therapeutic targets such as DNA, to peptide aggregates found in blood clots, neural fibrils, and membrane scaffolds. It is our belief that cleverly constructed frameworks with well-designed and controlled activation/reaction schemes can lead to novel therapeutics that can challenge evolving viral and bacterial invaders. From this evangelical perspective, our hope is that the conceptual framework, if not the specific designs in this Account, stimulate the readership to develop out-of-the-box therapeutic designs that may combat resistant disease targets.

Heterocyclic Nanographenes and Other Polycyclic Heteroaromatic Compounds: Synthetic Routes, Properties, and Applications

Two-dimensionally extended, polycyclic heteroaromatic molecules (heterocyclic nanographenes) are a highly versatile class of organic materials, applicable as functional chromophores and organic semiconductors. In this Review, we discuss the rich chemistry of large heteroaromatics, focusing on their synthesis, electronic properties, and applications in materials science. This Review summarizes the historical development and current state of the art in this rapidly expanding field of research, which has become one of the key exploration areas of modern heterocyclic chemistry.

Synthesis of 2-nitro-3-(pyrrol-1-yl)-5,10,15,20-tetraarylporphyrins via a Clauson-Kaas reaction and the study of their electronic properties

Versatile synthesis of new porphyrin building blocks, 2-nitro-3-(pyrrol-1-yl)-5,10,15,20-tetraarylporphyrins is described. These porphyrins demonstrate red shifted absorption bands and S₂ emission.

Ambient temperature synthesis of β,β′-fused nickel(ii) pyrrolo[1,2-a]pyrazinoporphyrins via a DBSA-catalyzed Pictet–Spengler approach

Synthesis of novel β,β′-fused nickel(ii) pyrrolo[1,2-a]pyrazinoporphyrins is accomplished for the first time at ambient temperature via a DBSA-catalyzed Pictet–Spengler approach.