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Magnetic circular dichroism (MCD) and UV-Vis-NIR spectroscopy were used to investigate the spectroscopic signatures of the triplet-multiplet and other transitions observed in the simplest [Formula: see text] (Pc^tBuCu and Pc^(SO3Na)4Cu) and [Formula: see text] (Pc^tBuV=O and TPz^(OAr)8V=O) phthalocyanine systems. Density Functional Theory (DFT) and time-dependent DFT (TDDFT) calculations allowed accurate correlation between the experimental and theoretical data. In particular, similarities between vibronic profiles in Q-band and triplet-multiplet band regions as well as the presence of MCD [Formula: see text]-terms associated with the 0-0 transitions support the relationship between the Q- and triplet-multiplet transitions. 

The electronic structures, charge-transfer, and triplet–multiplet transitions in cobalt(i), cobalt(ii), and cobalt(iii) phthalocyanines were investigated in detail by UV-vis-NIR, MCD, DFT, and TDDFT methods. 

In 1956, Elvidge and coworkers investigated the synthesis of a series of isoindoline compounds derived from phthalonitrile. They produced a series of secondary amine-modified isoindolines known as the imino(dialkylamino)isoindolines, and in this report, we revisit this chemistry. In addition to confirming the previously observed reactivity, we structurally characterized three examples and observed a double bond character between the isoindoline carbon atom and the secondary nitrogen atom position. This results in a rotational barrier about this bond, which we observed by NMR spectroscopy and probed using computational methods. The barriers are comparable to those seen in bis-substituted amides. 

The molecular structure of the unsubstituted iron(III) phthalocyanine [Formula: see text]-oxo(1) dimer ((PcFe)₂O) was determined by single crystal X-ray diffraction. In agreement with the earlier speculations, the dimer has a bent (Fe-O-Fe angle is 152.4[Formula: see text]) structure. The interplay between the [Formula: see text]-[Formula: see text] interactions and steric hindrances caused by the isoindole units led to the observed staggering angle of [Formula: see text]24[Formula: see text] between two phthalocyanine ligands. The high-spin iron(III) centers are located significantly above the phthalocyanine N4 planes (0.57–0.58 Å). Several DFT exchange-correlation functionals were used to calculate the absolute value and sign of the Mössbauer quadrupole splitting and antiferromagnetic coupling constant for X-ray determined geometry of (PcFe)₂O. It was demonstrated that the hybrid functionals provide the correct sign of the electric field gradient and the magnitude of the antiferromagnetic coupling constant compared to the pure functionals. 

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 T₁at 100 K, as well as the temperature dependence of T₁over the intermediate temperature range spanning [Formula: see text]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. 

Iron phthalocyanines play crucial fundamental and applied roles ranging from bulk colorants to components of advanced materials. In this mini-review, we discuss the influence of axial ligand identity on spectroscopic and redox properties of iron(ii) phthalocyanines. 

We report the template-based synthesis of a new series of ring-open phthalocyanine analogs that exhibit helical chirality. These conjugated helical porphyrinoids also strongly absorb across the entire visible spectrum.