Journal of Porphyrins and Phthalocyanines

This review presents typical examples of porphyrins, which serve as highly effective building blocks, primarily drawn from our past achievements. They function as both an electron donor and an energy donor/acceptor in various applications. These applications include photosynthetic and solar cell models, dye-sensitized solar cells, bulk heterojunction solar cells, and optogenetics based on photoinduced charge separation. Consequently, porphyrins are essential components for evaluating energy and electron transfer properties, as well as for energy and biological applications.

The modern era of photodynamic therapy (PDT) treatment of human cancer began in earnest in 1978, with the publication by Dougherty et al. of the first large series of humans with refractory or recurrent skin cancers successfully treated with PDT using HpD (Photofrin). The first human series of head and neck cancer patients successfully treated with PDT (Photofrin) was published in 1985, by Keller et al. Since that time, numerous clinical investigators around the world have treated thousands of head and neck cancer patients with PDT in clinical trials. These head and neck cancer PDT clinical trials enrolled patients with various stages of disease, and locations of the tumor and were treated using a variety of photosensitizers. Head and neck cancer PDT treatments were performed as the primary treatment with the intent to cure, as a late-stage treatment for palliation of the tumor, or as an adjuvant or neoadjuvant treatment in combination with surgery, radiation, chemotherapy and most recently immunotherapy. Over the past five decades, head and neck cancer PDT has evolved as newer and more targeted photosensitizers became available for clinical use, as well as advances in laser and fiberoptic technologies allowing for the activating light to be successfully and more easily delivered deep into large invasive tumors. In addition, PDT can be accurately delivered using endoscopic, robotic, CT, ultrasound and MRI guidance thereby specifically targeting the tumor and reducing treatment morbidity. Significant progress has been achieved in the ease of use and treatment efficacy of head and neck cancer PDT in various stages of the disease.

The detection of $\mathrm{\Delta }$-9-tetrahydrocannabinol (THC) is important for several applications from agriculture and pharmaceuticals to law enforcement. Two novel soluble zinc phthalocyanines were synthesized and their interaction with THC was studied. We report the change in the electrochemical and spectroelectrochemical response of the two zinc derivatives in the presence of THC using different organic solvents (DCM, THF, and DMF). The greatest change in spectroelectrochemical response was found when DCM was employed, whereas when THF was used an increase in higher energy $\pi$-$\pi$* transitions within the Pc cores was observed. Using DMF on the other hand demonstrated little change in response. We also found that the functional group used to solubilize the ZnPc played a significant role in the observed spectrochemical response to THC. These results demonstrate the potential for ZnPc-based chemical probes for the use in detection of THC.

A series of inner core $N$-alkylcorroles were synthesized and characterized. The introduction of both linear and branched alkyl groups was achieved, demonstrating the quite large scope of the reaction. Polyalkylation results in the formation of the $N$-21,$N$-22 regioisomer, although the introduction of the second alkyl group is less facile than previously observed in the case of the methyl substituent. Complete functionalization of the inner core nitrogens has been investigated, but only the N,N^′,N^″-trimethyl derivatives were obtained. The characterization of these species demonstrated a different arrangement of the methyl groups to the macrocyclic plane, which is peculiar when compared with the conformation of the analogous porphyrin derivatives. These $N$-alkylcorroles should prove to be of potential interest as ligands for various metal ions.

Hemoglobin (Hb) undergoes a well-documented R$\to$T quaternary transition from a high ${\mathrm{\text{O}}}_2$ affinity R state to a low ${\mathrm{\text{O}}}_2$ affinity T state to optimize ${\mathrm{\text{O}}}_2$ delivery to tissues. Also, red blood cells (RBCs) release a nitrovasodilator that increases blood flow to boost ${\mathrm{\text{O}}}_2$ delivery. Hb’s R$\to$T transition coordinates its ${\mathrm{\text{O}}}_2$ desaturation and RBC nitrovasodilator release by much-debated mechanisms. Here we investigate the allosterically controlled $S$-nitrosation of Hb at its conserved βCys93 (i.e., SNO-Hb formation) for nitrovasodilator release. First, we examined NO${}_2^{-}$/deoxyHb (HbFe^II) incubations following aeration to mimic RBC NO production by the nitrite reductase activity of HbFe^II and trapping of the nascent NO by βCys93 to give SNO-Hb on HbFe^II conversion to oxyHb (HbFeO₂). We confirmed SNO-Hb formation in the incubations with yields modulated by RBC antioxidant enzymes and ${\mathrm{\text{H}}}_2{\mathrm{\text{O}}}_2$ but not CO. Since FeO₂ hemes scavenge free NO, we hypothesized NO channeling within Hb and found by molecular dynamics simulations that most unligated NO molecules placed in the β-distal heme pocket (βDP) rapidly diffuse into a wide β-tunnel connecting the βDP to Hb’s central cavity and βCys93. Contraction of the central cavity brings NO closer to βCys93 in R-state plus βPhe71 and βTyr145 adopt conformations favorable to thiol access and SNO-Hb formation. In T-state, the SNO group is surface-exposed and destabilized to extrude NO. Thus, its structure, dynamics and conserved reactive thiol (βCys93) suggest that the β-subunit evolved to synergize ${\mathrm{\text{O}}}_2$ and nitrovasoactivity delivery to tissues as a function of Hb ${\mathrm{\text{O}}}_2$ saturation.

Electron spin superpositions represent a critical component of emergent quantum technologies in computation, sensing, encryption, and communication. However, spin relaxation (T₁) and decoherence (T_m) represent major obstacles to the implementation of molecular quantum bits (qubits). Synthetic strategies have made substantial progress in enhancing spin coherence times by minimizing contributions from surrounding electron and nuclear spins. For room-temperature operation, however, the lifetime of spin coherence becomes limited by coupling with vibrational modes of the lattice. Using pulse electron paramagnetic resonance (EPR) spectroscopy, we measure the spin-lattice relaxation of a vanadyl tetrapyrazinoporphyrazine complex appended with eight peripheral 2,6-diisopropylphenol groups (VOPyzPz-DIPP) and compare it to the relaxation of the archetypical vanadyl phthalocyanine molecular qubit (VOPc). The added peripheral groups lead to distinctly different spin relaxation behavior. While similar relaxation times are observed at low temperatures and ambient conditions, significant changes are observed for the orientation dependence of T₁ at 100 K, as well as the temperature dependence of T₁ over the intermediate temperature range spanning $\sim$10–150 K. These results can be tentatively interpreted as arising from loosened spin-phonon coupling selection rules and a greater number of accessible acoustic and optical modes contributing to the spin relaxation behavior of VOPyzPz-DIPP relative to VOPc.