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The computational description of correlated electronic structure, and particularly of excited states of many-electron systems, is an anticipated application for quantum devices. An important ramification is to determine the dominant molecular fragmentation pathways in photo-dissociation experiments of light-sensitive compounds, like sulfonium-based photo-acid generators used in photolithography. Here we simulate the static and dynamical electronic structure of the H$_3$S$^+$ molecule, taken as a minimal model of a triply-bonded sulfur cation, on a superconducting quantum processor of the IBM Falcon architecture. To this end, we generalize a qubit reduction technique termed entanglement forging or EF [A. Eddins et al., Phys. Rev. X Quantum, 2022, 3, 010309], currently restricted to the evaluation of ground-state energies, to the treatment of molecular properties. While in a conventional quantum simulation a qubit represents a spin-orbital, within EF a qubit represents a spatial orbital, reducing the number of required qubits by half. We combine the generalized EF with quantum subspace expansion [W. Colless et al, Phys. Rev. X, 2018, 8, 011021], a technique used to project the time-independent Schrodinger equation for ground and excited states in a subspace. To enable experimental demonstration of this algorithmic workflow, we deploy a sequence of error-mitigation techniques. We compute dipole structure factors and partial atomic charges along the ground- and excited-state potential energy curves, revealing the occurrence of homo- and heterolytic fragmentation. This study is an important step towards the computational description of photo-dissociation on near-term quantum devices, as it can be generalized to other photodissociation processes and naturally extended in different ways to achieve more realistic simulations., 13 pages, 7 figures

Solid-state photodecarbonylation is an attractive but underutilized methodology to forge hindered C−C bonds in complex molecules. This study discloses the use of this reaction to assemble the vicinal quaternary stereocenter motif present in bis(cyclotryptamine) alkaloids. Our strategy was enabled by experimental and computational investigations of the role of substrate conformation on the success or failure of the solid-state photodecarbonylation reaction. This informed a crystal engineering strategy to optimize the key step of the total synthesis. Ultimately, this endeavor culminated in the successful synthesis of the bis(cyclotryptamine) alkaloid “psychotriadine,” which features the elusive piperidinoindoline framework. Psychotriadine, a previously unknown compound, was identified in the extracts of the flower Psychotria colorata, suggesting it is a naturally occurring metabolite.

Amphidynamic crystals, which possess crystallinity and support dynamic behaviours, are very well suited to the exploration of emergent phenomena that result from the coupling on the dynamic moieties. Here, dipolar rotors have been embedded in a crystalline metal–organic framework. The material consists of Zn(ii) nodes and two types of ditopic bicyclo[2.2.2]octane-based linkers—one that coordinates to the Zn clusters through two 1,4-aza moieties, and a difluoro-functionalized derivative (the dipolar rotor) that coordinates through linked 1,4-dicarboxylate groups instead. Upon cooling, these linkers collectively order as a result of correlated dipole–dipole interactions. Variable-temperature, frequency-dependent dielectric measurements revealed a transition temperature Tc = 100 K, when a rapidly rotating, dipole-disordered, paraelectric phase transformed into an ordered, antiferroelectric one in which the dipole moments of the rotating linkers largely cancelled each other. Monte Carlo simulations on a two-dimensional rotary lattice showed a ground state with an Ising symmetry and the effects of dipole–lattice and dipole–dipole interactions. A metal–organic framework (MOF) has been prepared that features dynamic rotors embedded within its crystalline lattice. The dipolar F2-functionalized carboxylate linkers—rapidly rotating at room temperature—show correlated behaviour upon cooling, converting the paraelectric MOF into an ordered antiferroelectric one below 100 K.

We report the synthesis and rotational dynamics of the pillared metal–organic framework Zn2(F2BDC)2(DABCO) where F2BDC = 2,3-difluorobenzene-1,4-dicarboxylate acts as a rotating dipolar linker and ...

In this review we highlight the recent efforts towards the development of molecular gears with an emphasis on building molecular gears in the solid state and the role that molecular gearing and correlated motions may play in the function of crystalline molecular machines. We discuss current molecular and crystal engineering strategies, challenges associated with engineering correlated motion in crystals, and outline experimental and theoretical tools to explore gearing dynamics while highlighting key advances made to date., Here we highlight recent efforts towards the development of molecular gears in the solid state and the role that molecular gearing and correlated motions may play in the function of crystalline molecular machines.

Molecular spur gear dynamics with high gearing fidelity can be achieved through a careful selection of constituent molecular components that favorably position and maintain the two gears in a meshed configuration. Here, we report the synthesis of a new macrocyclic molecular spur gear with a bibenzimidazole stator combined with a second naphthyl bis-gold-phosphine gold complex stator to place two 3-fold symmetric 9,10-diethynyl triptycene cogs at the optimal distance of 8.1 A for gearing. Micro electron diffraction (μED) analysis confirmed the formation of the macrocyclic structure and the proper alignment of the triptycene cogs. Gearing dynamics in solution are predicted to be extremely fast and, in fact, were too fast to be observed with variable-temperature 1H NMR using CD2Cl2 as the solvent. A combination of molecular dynamics and metadynamics simulations predict that the barriers for gearing and slippage are ca. 4 kcal mol-1 and ca. 9 kcal mol-1, respectively. This system is characterized by enhanced gearing fidelity compared to the acyclic analog. This is achieved by rigidification of the structure, locking the two triptycenes in the preferred gearing distance and orientation.

WB4.2 is one of the hardest metals known. Though not harder than diamond and cubic boron nitride, it surpasses these established hard materials in being cheaper, easier to produce and process, and also more functional. Metal impurities have been shown to a?ct and in some cases further improve the intrinsic hardness of WB4.2, but the mechanism of hardening remained elusive. In this work we ?first theoretically elucidate the preferred placements of Ti, V, Cr, Mn, Zr, Nb, Mo, Hf, Ta in the WB4.2 structure, and show these metals to preferentially replace W in two competing positions with respect to the partially occupied B3 cluster site. The impurities avoid the void position in the structure. Next, we analyze the chemical bonding within these identifi?ed doped structures, and propose two different mechanisms of strengthening the material, afforded by these impurities, and dependent on their nature. Smaller impurity atoms (Ti, V, Cr, Mn) with deeply lying valence atomic orbitals cause the inter-layer compression of WB4.2, which strengthens the Bhex–Bcluster bonding slightly. Larger impurities (Zr, Nb, Mo, Hf, Ta) with higher-energy valence orbitals, while expanding the structure and negatively impacting the Bhex–Bcluster bonding, also form strong Bcluster–M bonds. The latter effect is an order of magnitude more substantial than the effect on the Bhex–Bcluster bonding. We conclude that the e effect of the impurities on the boride hardness does not simply reduce to structure interlocking due to the size difference between M and W, but instead, has a significant electronic origin.

The rotational dynamics of dirhodium supramolecular gears, formed with four 9-triptycene carboxylates cyclically arranged around a dirhodium core with variable axial ligands as originally designed by Shionoya

Photoexcitation can lead to either homogeneous or heterogeneous transformations of a reactive surface. Homogeneous transformations result in a statistical mixture of reactants and products, whereas the outcome of heterogeneous transformations is a coexistence of macroscopic reactant and product domains, separated by a phase boundary. Heterogeneous photoinduced changes are also typically restricted to the surface, have individual phase structures that are inaccessible with classical diffraction methods, and possess surface properties that cannot readily be measured by the traditional wetting (water contact angle) technique. In this study, we demonstrate application of Atomic Force Microscopy (AFM) to obtain high spatial resolution surface energy distribution in the trans and cis domains on the surface of azobenzene single crystal. UV excitation of single crystals of 3′,4′-dimethyl-4-(dimethylamino)azobenzene results in domino-like trans-to-cis isomerization on their surface. In the AFM phase channel, this ...

The photochemical conversion of 1,8a-dihydroazulene-1,1-dicarbonitrile (DHA) to vinylheptafulvene (VHF) is a positive T-type photoswitch that is well understood in solution, but has not been explored in the solid state. Upon excitation with UV light, DHA is converted into VHF in the solid state, with a distinct color change from yellow to deep-red, and retention of crystallinity. The structure of the ring-opened product was assigned to syn-VHF using variable-temperature infrared spectroscopy, and determined by X-ray photodiffraction in a crystal enriched with the product by two-photon excitation. A radical pathway becomes an observable photoreaction channel at low temperatures, and includes a strongly colored, short-lived diradical intermediate.