Haruyuki Nakano

Cobalt (Co) complexes of porphyrin derivatives possess distinctive redox properties, and hence, their development has attracted significant interest across a wide range of fields. Herein, we report the new examples of the Co complexes of 5,15‐diazaporphyrin (DAP) and 5‐monoazaporphyrin (MAP) derivatives bearing meso ‐aryl groups. These Co complexes were prepared by metal‐templated cyclization of Co–bis(dipyrrin) complexes, complexation of azaporphyrin freebases with a Co salt, and meso ‐N‐functionalization of the Co complexes of DAP and MAP with diphenyliodonium hexafluorophosphate or methyl triflate. The structures as well as the optical and redox properties of these new Co complexes were elucidated by X‐ray crystallography, spectroscopic and voltammetric measurements, and density functional theory calculations. The introduction of a positive charge to the DAP and MAP rings via meso ‐N‐functionalization considerably altered the frontier‐orbital energies, resulting in redshifts of the Q bands and anodic shifts of the ligand‐centered redox processes. The addition of axial ligands also had notable effects on the metal‐centered and ligand‐centered redox processes. All the Co ^II complexes catalyzed the intramolecular radical cyclization and 1,2‐H‐shift reactions of N ‐benzyl‐ N ‐Boc‐3‐diazopropane‐1‐amine in the presence of Cs ₂ CO ₃ to yield two kinds of products via the corresponding σ‐bonded alkyl Co‐azaporphyrin intermediates.

Adaptive multiscale simulations, such as adaptive quantum mechanics (QM)/molecular mechanics (MM), are indispensable for investigating complex solution dynamics but historically suffer from a fundamental dilemma: the dynamic exchange of identical solvent molecules across different model resolutions introduces an energetic asymmetry under solvent exchange (specifically, a permutation asymmetry where physically identical molecules are treated indistinguishably yet subjected to different force fields depending on their instantaneous positions). This asymmetry forces a prohibitive trade-off between severe structural distortions and the violation of Hamiltonian conservation (continuous energy drift). To resolve this issue, we propose the “Integrated Molecular Model,” a paradigm-shifting framework that unifies multiple resolutions into a single, dynamically consistent potential. By employing a neural network that takes only the multiscale weight functions as input descriptors, our model learns to systematically cancel the nonphysical transition forces originating from spatial discontinuities. As a proof-of-concept, we validated this unified framework on bulk water, aqueous ionic solutions, and reactive hydronium ions. Our approach not only faithfully restores artifact-free solvation structures but also strictly conserves the Hamiltonian, enabling stable, long-term simulations under the microcanonical (NVE) ensemble. Consequently, the model successfully eliminates artificial thermostat-induced breathing modes, allowing for the rigorous evaluation of intrinsic dynamical properties such as diffusion coefficients. Furthermore, owing to its physically informed network design, the correction potential introduces less than 2% additional computational overhead and demonstrates remarkable zero-shot transferability across chemically similar ionic species. By eradicating the inherent asymmetry of adaptive multiscale modeling, this highly scalable framework establishes a robust foundation for high-fidelity simulations of complex condensed-phase phenomena, including reactive dynamics at solid–liquid interfaces and ion transport in battery electrolytes.

Adaptive multiscale simulations, such as adaptive QM/MM, are indispensable for investigating complex solution dynamics but historically suffer from a fundamental dilemma: the dynamic exchange of identical solvent molecules across different model resolutions introduces an energetic asymmetry under solvent exchange (specifically, a permutation asymmetry where physically identical molecules are treated indistinguishably yet subjected to different force fields depending on their instantaneous positions). This asymmetry forces a prohibitive trade-off between severe structural distortions and the violation of Hamiltonian conservation (continuous energy drift). To resolve this issue, we propose the ”Integrated Molecular Model,” a paradigm-shifting framework that unifies multiple resolutions into a single, dynamically consistent potential. By employing a neural network that takes only the multiscale weight functions as input descriptors, our model learns to systematically cancel the non-physical transition forces originating from spatial discontinuities. As a proof-of-concept, we validated this unified framework on bulk water, aqueous ionic solutions, and reactive hydronium ions. Our approach not only faithfully restores artifact-free solvation structures but also strictly conserves the Hamiltonian, enabling unprecedentedly stable, long-term simulations under the microcanonical (NVE) ensemble. Consequently, the model successfully eliminates artificial thermostat-induced breathing modes, allowing for the rigorous evaluation of intrinsic dynamical properties such as diffusion coefficients. Furthermore, owing to its physically informed network design, the correction potential introduces less than 2% additional computational overhead and demonstrates remarkable zero-shot transferability across chemically similar ionic species. By eradicating the inherent asymmetry of adaptive multiscale modeling, this highly scalable framework establishes a robust foundation for high-fidelity simulations of complex condensed-phase phenomena, including reactive dynamics at solid-liquid interfaces and ion transport in battery electrolytes.

Adaptive multiscale simulations, such as adaptive QM/MM, are indispensable for investigating complex solution dynamics but historically suffer from a fundamental dilemma: the dynamic exchange of identical solvent molecules across different model resolutions introduces a physical asymmetry. This asymmetry forces a prohibitive trade-off between severe structural distortions and the violation of Hamiltonian conservation (continuous energy drift). To definitively resolve this issue, we propose the ”Integrated Molecular Model,” a paradigm-shifting framework that mathematically unifies multiple resolutions into a single, dynamically consistent potential. By employing a neural network that takes only the multiscale weight functions as input descriptors, our model learns to systematically cancel the non-physical transition forces originating from spatial discontinuities. As a proof-of-concept, we validated this unified framework on bulk water, aqueous ionic solutions, and reactive hydronium ions. Our approach not only faithfully restores artifact-free solvation structures but also strictly conserves the Hamiltonian, enabling unprecedentedly stable, long-term simulations under the microcanonical (NVE) ensemble. Consequently, the model successfully eliminates artificial thermostat-induced breathing modes, allowing for the rigorous evaluation of intrinsic dynamical properties such as diffusion coefficients. Furthermore, owing to its physically informed network design, the correction potential introduces less than 2\% additional computational overhead and demonstrates remarkable zero-shot transferability across chemically similar ionic species. By fundamentally eradicating the inherent asymmetry of adaptive multiscale modeling, this highly scalable framework establishes a robust foundation for high-fidelity simulations of complex condensed-phase phenomena, including reactive dynamics at solid-liquid interfaces and ion transport in battery electrolytes.

In variational quantum algorithms, parameterization is typically applied to single-qubit gates. In this study, we instead parameterize a generalized controlled gate and propose an algorithm to locally minimize the cost function by maximally optimizing these parameters. This method extends the Free Quaternion Selection (FQS) technique, which was originally developed for singlequbit gate optimization. To evaluate its performance, we apply the proposed method to a variety of quantum optimization tasks, including the Variational Quantum Eigensolver (VQE) for both Ising and molecular Hamiltonians, fidelity maximization in general variational quantum algorithms (VQAs), and unitary compilation of time evolution operators. Across these applications, our method demonstrates efficient optimization, enhanced expressibility, and the ability to construct shallower circuits compared to existing techniques. Moreover, the method can be generalized to optimize particle-number-conserving gates, which are particularly relevant for quantum chemistry. Leveraging this capability, we further demonstrate that the method achieves superior quantum compilation of molecular time-evolution operators by approximating them with shallower circuits than standard Trotter decomposition.

In contrast to the great advances of phthalocyanine‐based materials, the potential of 5,10,15‐triazaporphyrins has not been realized because of the lack of fundamental information about their structure‐property relationships. Here, we report new derivatives of dibenzo‐5,10,15‐triazaporphyrin (DBTriAP) with aryl or alkyl substituents at the meso and/or β positions. Freebases of DBTriAP were prepared by the condensation of two types of 1,9‐dibromodipyrrins with 1,3‐diiminoisoindoline and subsequent functionalization of the β‐pyrrolic carbons. Zinc(II) complexes of DBTriAP were obtained by complexation of the corresponding freebases with zinc(II) acetate. The optical and electrochemical properties of the DBTriAP derivatives were studied by steady‐state and transient ultraviolet/visible absorption/emission spectroscopy, magnetic circular dichroism spectroscopy, cyclic voltammetry (CV), and density functional theory (DFT) calculations. Replacing the β‐pyrrolic hydrogens of the 5‐mesityl‐DBTriAP derivatives with aryl groups resulted in substantial red shifts of the low‐energy absorption band because of the effective π‐delocalization and/or charge‐transfer interaction with the DBTriAP chromophore. The 2,3,17,18‐tetraethyl‐DBTriAP freebase exhibited split redox processes in its cyclic voltammogram, suggesting the rapid formation of a π‐stacked dimer radical cation facilitated by the highly planar structure. Most of the DBTriAP derivatives emitted red fluorescence with quantum yields of 0.07–0.31, indicating their potential as luminescent materials.

The first examples of 6,21-diaza-m-benziporphyrin (R₂DABP) and 6,21-diaza-m-pyriporphyrin (Ph₂DAPP) with methyl or phenyl groups on the meso nitrogen atoms, along with new examples of dioxa-m-benziporphyrin, are reported. The metal complexes of R₂DABP and Ph₂DAPP exhibit red-shifted optical absorption bands that extend into the near-infrared region, compared to their corresponding freebase forms. NMR spectroscopy reveals that the metalation of the freebase of Ph₂DAPP enhances the paratropic ring-current effect originating from the pseudo 20π-electron macrocyclic pathway.

Porphyrinoids in the 20π‐electron state have been extensively studied from the fundamental viewpoint of investigating their structure–antiaromaticity relationships. However, most of the 20π porphyrinoids are highly distorted and unstable in air, which hinder the comprehensive analysis of paratropic ring‐current effects derived from planar π‐electron systems. Herein, we present the first examples of antiaromatic Sn(IV) complexes of 5,10,15,20‐tetraaryl‐5,15‐diazaporphyrinoids (SnX₂TADAPs), prepared by the complexation of the corresponding freebases with Sn(II) chloride under aerobic conditions and subsequent metathesis of the axial ligands, that show paratropic ring‐current effects. Notably, both neutral 20π‐electron derivatives and 19π‐electron radical cations of SnX₂TADAP are extremely stable in air owing to the intrinsic electronic effects of the central Sn(IV) unit and meso nitrogen atoms. NMR spectroscopy, cyclic voltammetry, and density functional theory calculations were performed to assess the ring‐current effects and orbital energies of a series of the 20π‐electron SnX₂TADAPs, and the results reveal that the paratropic ring‐current effects arising from the planar 20π‐electron DAP ring increases with a decrease in the HOMO–LUMO energy gap.

Despite the significant development and extensive application of phthalocyanine and related azaporphyrins, little attention has been paid to meso‐N‐substituted azaporphyrinoids. Here, we report new derivatives of 5,10,20‐triaryl‐5,15‐diazaporphyrinoids (Ar₃DAP), which are reversibly redox‐switchable between the 18π‐ and 19π‐electron state. Four kinds of metal(II) complexes and free bases of Ar₃DAP were prepared by metal‐templated cyclization of metal(II) complexes of 5,10,15‐triaryl‐10‐azabiladiene‐ac with sodium azide or copper‐catalyzed N‐phenylation of 10,20‐diaryl‐5,15‐diazaporphyrins (Ar₂DAP) with diphenyliodonium hexafluorophosphate. In particular, regioselective N‐phenylation of covalently linked Ar₂DAP dimer afforded two kinds of dimers bearing one or two meso‐N‐phenyl groups. Cyclic voltammetry revealed that attaching one aryl group onto the meso‐nitrogen atom markedly changed the redox potentials of the DAP ring. The aromaticity and optical properties of the new Ar₃DAP π‐electron systems were assessed using various spectroscopic measurements and density functional theory calculations. The distribution pattern of an electron spin in the neutral Ar₂DAP–Ar₃DAP radical revealed that the meso‐N‐phenyl group had a remarkable effect on spin delocalization of DAP π‐radical. The present study provides valuable information for understanding the effects of the number of meso‐N‐substituents on azaporphyrin‐based π‐electron systems.