Conformational effects, molecular orbitals, and reaction activities of bis(phthalocyaninato) lanthanum double-deckers: density functional theory calculations

Machine Learning and Quantum Calculation for Predicting Yield in Cu-Catalyzed P-H Reactions

The paper discussed the use of machine learning (ML) and quantum chemistry calculations to predict the transition state and yield of copper-catalyzed P-H insertion reactions. By analyzing a dataset of 120 experimental data points, the transition state was determined using density functional theory (DFT). ML algorithms were then applied to analyze 16 descriptors derived from the quantum chemical transition state to predict the product yield. Among the algorithms studied, the Support Vector Machine (SVM) achieved the highest prediction accuracy of 97%, with over 80% correlation in Leave-One-Out Cross-Validation (LOOCV). Sensitivity analysis was performed on each descriptor, and a comprehensive investigation of the reaction mechanism was conducted to better understand the transition state characteristics. Finally, the ML model was used to predict reaction plans for experimental design, demonstrating strong predictive performance in subsequent experimental validation.

Effects of aggregation on the structures and excited-state absorption for zinc phthalocyanine

In the present paper, the aggregated structures of zinc phthalocyanine (ZnPc) have been investigated by considering its dimers and trimers. Based on the density functional theory calculations, two stable conformations are obtained for the ZnPc dimer and trimer, respectively. The IGMH (independent gradient model based on the Hirshfeld partition of molecular density) analysis reveals that the π-π interaction between the ZnPc molecules causes the aggregation. Normally, stacked structures with a slight displacement are favorable for aggregation. In addition, the planar structure of the ZnPc monomer is largely maintained in the aggregated conformations. For the presently obtained structures, the first singlet excited state absorption (ESA) spectra of these aggregated conformations of ZnPc were calculated based on the linear-response time-dependent density functional theory (LR-TDDFT), which has been well applied by our group. The results of the excited state absorption spectra reveal that the aggregation causes the ESA band to blue shift compared to the ZnPc monomer. By using the conventional description of the interaction between monomer transition dipoles, this blue shift is elucidated by the side-by-side transition dipole moments in the constituted monomers. The present results for the ESA combined with the previously reported results for ground state absorption (GSA) will provide guidelines to tune the window of the optical-limiting effect for the ZnPc based materials.

Redox-Triggered Switching of Conformational State in Triple-Decker Lanthanide Phthalocyaninates

Double- and triple-decker lanthanide phthalocyaninates exhibit unique physical-chemical properties, particularly single-molecule magnetism. Among other factors, the magnetic properties of these sandwiches depend on their conformational state, which is determined via the skew angle of the phthalocyanine ligands. Thus, in the present work we report the comprehensive conformational study of substituted terbium(III) and yttrium(III) trisphthalocyaninates in solution depending on the substituents at the periphery of molecules, redox-states and nature of solvents. Conjunction of UV-vis-NIR spectroscopy and quantum-chemical calculations within simplified time-dependent DFT in Tamm-Dancoff approximation provided the spectroscopic signatures of staggered and gauche conformations of trisphthalocyaninates. Altogether, it allowed us to demonstrate that the butoxy-substituted complex behaves as a molecular switcher with controllable conformational state, while the crown-substituted triple-decker complex maintains a staggered conformation regardless of external factors. The analysis of noncovalent interactions within the reduced density gradient approach allowed to shed light on the nature of factors stabilizing certain conformers.

Luminescent Complexes of Europium (III) with 2-(Phenylethynyl)-1,10-phenanthroline: The Role of the Counterions

New antenna ligand, 2-(phenylethynyl)-1,10-phenanthroline (PEP), and its luminescent Eu (III) complexes, Eu(PEP)₂Cl₃ and Eu(PEP)₂(NO₃)₃, are synthesized and characterized. The synthetic procedure applied is based on reacting of europium salts with ligand in hot acetonitrile solutions in molar ratio 1 to 2. The structure of the complexes is refined by X-ray diffraction based on the single crystals obtained. The compounds [Eu(PEP)₂Cl₃]·2CH₃CN and [Eu(PEP)₂(NO₃)₃]∙2CH₃CN crystalize in monoclinic space group P2_1/n and P2_1/c, respectively, with two acetonitrile solvent molecules. Intra- and inter-ligand π-π stacking interactions are present in solid stat and are realized between the phenanthroline moieties, as well as between the substituents and the phenanthroline units. The optical properties of the complexes are investigated in solid state, acetonitrile and dichloromethane solution. Both compounds exhibit bright red luminescence caused by the organic ligand acting as antenna for sensitization of Eu (III) emission. The newly designed complexes differ in counter ions in the inner coordination sphere, which allows exploring their influence on the stability, molecular and supramolecular structure, fluorescent properties and symmetry of the Eu (III) ion. In addition, molecular simulations are performed in order to explain the observed experimental behavior of the complexes. The discovered structure-properties relationships give insight on the role of the counter ions in the molecular design of new Eu (III) based luminescent materials.

Heteroleptic Crown-Substituted Tris(phthalocyaninates) as Dynamic Supramolecular Scaffolds with Switchable Rotational States and Tunable Magnetic Properties

Herein we report single-crystal X-ray diffraction characterization and complementary solution studies of supramolecular interaction between potassium salts and heteroleptic homo- and heteronuclear triple-decker crown phthalocyaninates [(15C5)₄Pc]M*[(15C5)₄Pc]M(Pc) or [M*,M], where M* and M = Y and/or Tb. Our results evidence that, in contrast to the previously studied crown-substituted phthalocyanines, the interaction of K⁺ cations with [M*,M] does not induce their intermolecular aggregation. Instead, the cations reversibly intercalate between the crown-substituted phthalocyanine ligands, resulting in switching of the coordination polyhedron of the metal center M* from square-antiprismatic to square-prismatic. In the case of terbium(III) complexes, such a switching alters their magnetic properties, which can be read-out by ¹H NMR spectroscopy. For [Tb*,Y], such a switching causes an almost 25% increase in the axial component of the magnetic susceptibility tensor. Even though the polyhedron of the paramagnetic center in [Y*,Tb] is not switched, minor structural perturbations associated with the overall reorganization of the receptor also cause smaller, but nevertheless appreciable, growth of the axial anisotropy. The observed effects render the studied complexes as molecular switches with tunable magnetic properties.

Identification of Main Active Sites and the Role of NO2 on NOx Reduction with CH4 over In/BEA Catalyst: A Computational Study

The main active sites and the catalytic process in selective catalytic reduction of NOx by CH4 (CH4-SCR) on In/BEA catalyst were investigated by density functional theory (DFT) using a periodic model. The [InO]+ and [InOH]2+ moieties were constructed in the channel of periodic BEA zeolite representing the Lewis and Brønsted acid sites. The electronic structures [InO]+ and [InOH]2+ were analyzed, and it was found that the [InO]+ group were the main active sites for CH4 activation and NO/NO2 adsorption in the CH4-SCR process. CH4 molecules could be activated on the O site of the [InO]+ group in In/BEA, which was resulted from the strong interactions between the C-p orbital of the CH4 molecule and the O-p orbital of the [InO]+ group. CH4 activation was the initial step in CH4-SCR on In/BEA catalyst. NO2 molecules were essential in the SCR process, and they could be produced by NO reacting with gaseous O2 or the O atom of the [InO]+ group. The presence of NO2 could facilitate the key intermediate nitromethane (CH3NO2) formation and lower the reaction barrier in the SCR process.

Elucidating π–π interaction-induced extension effect in sandwich phthalocyaninato compounds

π–π interaction-linked extension in the perpendicular direction to the monomers and corresponding effect on nonlinear optic properties have been clearly disclosed over the multiple-decker sandwich-type phthalocyaninato metal compounds.

Anomalously Large Spectral Shifts near the Quantum Tunnelling Limit in Plasmonic Rulers with Subatomic Resolution

The resonance wavelength of a coupled plasmonic system is extremely sensitive to the distance between its metallic surfaces, resulting in "plasmon rulers". We explore this behavior in the subnanometer regime using self-assembled monolayers of bis-phthalocyanine molecules in a nanoparticle-on-mirror (NPoM) construct. These allow unprecedented subangstrom control over spacer thickness via choice of metal center, in a gap-size regime at the quantum-mechanical limit of plasmonic enhancement. A dramatic shift in the coupled plasmon resonance is observed as the gap size is varied from 0.39 to 0.41 nm. Existing theoretical models are unable to account for the observed spectral tuning, which requires inclusion of the quantum-classical interface, emphasizing the need for new treatments of light at the subnanoscale.

Fluorescent probes guided by a new practical performance regulation strategy to monitor glutathione in living systems

A practical regulation strategy for the design of glutathione specific probes and their application in living systems.

Glutathione (GSH) plays an important role in the body's biochemical defense system, and the detection of GSH in a physiological system is an important tool for understanding redox homeostasis. Protection–deprotection strategies have proven to be the most reliable, among existing detection methods. However, the understanding of how various electronic and steric effects influence a probe's ability to recognize a substrate is still lacking. In this study, we have analyzed various substituent effects on a GSH probe template via theoretical calculations and constructed the performance regulation and control strategy for this kind of probe. We then developed a series of guided probes using eighteen different acrylic ester derivatives to mask the fluorescence of fluorescein. The optical performance differences between the guided probes strongly supported the applicability of our proposed guiding strategy. Moreover, the positively guided probes are excellent for imaging GSH distribution in living cells and mice.

Detection and Manipulation of Charge States for Double-Decker DyPc2 Molecules on Ultrathin CuO Films

Charge states of lanthanide double-decker phthalocyanines complexes significantly influence their geometrical structures and magnetic properties. In this study, the charge states of single DyPc₂ molecules on an ultrathin CuO film were detected by scanning tunneling microscopy and spectroscopy in magnetic fields. Four types of adsorptions of DyPc₂ molecules on CuO were experimentally observed. Without applying voltages, two of them were positively charged with the other two at the neutral state. By controlling the sample bias, two types of neutral molecules can be switched to the positively and negatively charged states, respectively. This manipulation was not realized for the DyPc₂ cations. A way to precisely detect the molecular charge states with and without current is beneficial for the development of molecular electronics.

Room temperature chiral reorganization of interfacial assembly of achiral double-decker phthalocyanine

Chiral reorganization with amplification of the Cotton effect is achieved at room temperature and atmospheric pressure in the solid-state.

Scanning tunnelling spectroscopy and manipulation of double-decker phthalocyanine molecules on a semiconductor surface

A scanning tunnelling microscope (STM) operated at 5 K was used to study dysprosium biphthalocyanine (DyPc₂) molecules adsorbed on the inert III-V semiconductor surface InAs(1 1 1)A. Orbital imaging and scanning tunnelling spectroscopy measurements reveal that the molecular electronic structure remains largely unperturbed, indicating a weak molecule-surface binding. The molecule adsorbs at the In vacancy site of the (2  ×  2)-reconstructed surface and is highly sensitive to current-induced excitations leading to random rotational fluctuations. Owing to the weak surface binding, individual molecules can be precisely repositioned and arranged by the STM tip via attractive tip-molecule interaction. In this way, DyPc₂ dimers of well-defined internal structure can be assembled which exist in two conformations of equivalent appearance. A binary switching between these two conformers can be induced by injecting electrons into one of the two molecules. The conformational change of the dimer proceeds via a concerted molecular rotation and minor lateral displacement. The synchronised switching observed here is attributed to steric interactions between the two molecules constituting the dimer.

DFT characterization on the mechanism of sulfoxidation with H2O2 catalyzed by tetranuclear peroxotungstates [XO4{WO(O2)2}4](n-) (X = Si(IV), P(V), S(VI), As(V), and Se(VI))

A thorough theoretical analysis was carried out on the sulfoxidation with H2O2 catalyzed by a tetranuclear peroxotungstate [SiO4{WO(O2)2}4](4-). The active species is the [SiO4{WO(O2)2}4(H2O2)](4-) (SiW4(H2O2)) complex rather than [SiO4{WO(O2)2}4](4-) (SiW4). The catalytic cycle consists of three elementary processes: oxygen transfer, sulfoxide dissociation, and catalyst regeneration. The oxygen transfer occurs from the peroxo oxygen atom O1 of SiW4(H2O2) to the sulfur center of dimethyl sulfide with a moderate Gibbs activation energy (ΔG°(‡)) of 17.1 kcal mol(-1). By comparing potential energy surfaces and condensed Fukui functions (ƒ(+)), the electrophilicity of the outer peroxo atoms in SiW4(H2O2) determines which oxygen transfers to the dimethyl sulfide. Then, the sulfoxide dissociation proceeds with a small ΔG°(‡) value of 2.3 kcal mol(-1) by elongation of the peroxo O1-O4 distance and elimination of the product dimethylsulfoxide. Finally, the catalyst regeneration is found to occur via two successive proton transfers from H2O2 to the oxygen atoms of peroxotungstates with the ΔG°(‡) values of 15.9 and 15.3 kcal mol(-1), which has been firstly examined in the present study. All of these steps occur easily with moderate ΔG°(‡) values, but the oxygen transfer is the rate-determining step of this catalytic reaction. In addition, the catalytic activity of peroxotungstates can be effectively tuned by changing the heteroatom X of [XO4{WO(O2)2}4(H2O2)](n-) in the order: Se(VI) ≈ S(VI) > As(V) ≈ P(V) > Si(IV).

Theoretical studies on oxidation-switchable second-order nonlinear optical responses of Metallosalen-Keggin polyoxometalate derivatives

The one-electron oxidation effect on the first hyperpolarizability of Metallosalen-Keggin polyoxometalate derivatives.

Low-temperature scanning tunneling microscopy study on the electronic properties of a double-decker DyPc2 molecule at the surface

Inaccessibility of the Dy 4f states in the double-decker DyPc₂ molecule, as evidenced by dI/dV mapping in the constant height mode.

Novel 3,6-unsymmetrically disubstituted-1,2,4,5-tetrazines: S-induced one-pot synthesis, properties and theoretical study

18 unprecedented 3,6-unsymmetrically disubstituted-1,2,4,5-tetrazines were synthesized, and their spectral and electrochemical properties are studied. A systematic theoretical investigation based on DFT calculations was carried out.

Density functional theory prediction for the second-order nonlinear optical responses of phenanthroline-fused phthalocyanine derivatives

A series of unsymmetrical phenanthroline-fused phthalocyanine derivatives including Zn [ Pc ( Phen )], Zn [ Pc ( Phen )2], Zn [ Pc ( Phen )3], Zn [ Pc ( NH 2)6( Phen )], Zn [ Pc ( NH 2)4( Phen )2], Zn [ Pc ( NH 2)2( Phen )3], Zn [ PcF 6( Phen )], Zn [ PcF 4( Phen )2], and Zn [ PcF 2( Phen )3] were designed to explore their properties of geometric and electronic structures, electronic absorption spectra, and second-order nonlinear responses under density functional theory and time-dependent density functional theory calculations. The computational results show that the peripheral substituents with push-pull effect could obviously change the π–π* transitions, leading to a tunable absorption region in the range between 300–800 nm. The hyperpolarizabilities were carefully investigated using CP-DFT method, revealing the size effect and clarifying the limit when expanding the conjugated system is employed to improve the hyper-Rayleigh scattering response coefficient (βHRS). According to the results, the NH 2-substitued phenanthroline-fused phthalocyanines are considered as ideal NLO blocking materials with large βHRS.

13C NMR aided design of molecularly imprinted adsorbents for selectively preparative separation of erythromycin

Based on the ¹³C chemical shift changes, the optimal monomer of MAA was selected and the rational binding sites were predicted. The resultant materials show good selectivity for erythromycin.

Reversible chiral switching of bis(phthalocyaninato) terbium(III) on a metal surface

We demonstrate a reversible chiral switching of bis(phthalocyaninato) terbium(III) molecules on an Ir(111) surface by low temperature scanning tunneling microscopy. With an azimuthal rotation of its upper phthalocyanine ligand, the molecule can be switched between a chiral and an achiral configuration actuated by respective inelastic electron tunneling and local current heating. Moreover, the molecular chiral configuration can be interchanged between left and right handedness during the switching manipulations, thereby opening up potential nanotechnological applications.

Design of a universal reversible bidirectional current switch based on the fullerene-phthalocyanine supramolecular system

A novel bidirectional current ON-OFF switch controlled by electron injection and deprivation was proposed on the basis of the density functional theory (DFT) calculation over a fullerene-phthalocyanine supramolecular system PcCoC(60) for the first time. The electron density for PcCoC(60) was revealed to move from fullerene to phthlocyanine only in the oxidized form and from phthlocyanine to fullerene only in the reduced form, reaching the control of electron movement direction by changing the oxidation state of this supramolecular system.

A special conjugated model around sp3 carbon atoms: density functional theory study on the homoaromatic electron delocalization and applications of benzo-fused tetra(triptycene)porphyrins

The three-unit homoaromatic electron-delocalizing nature of the benzo-fused tetra(triptycene)porphyrins (TTPs) with a three-dimensional conjugated model is clarified using density functional theory studies. Due to the electron delocalization, the unidirectional photon-induced current of this kind of TTP molecular skeleton with a highest efficiency of about 90% in the range between 350 and 500 nm gives them great potential as efficient solar antenna collectors. In addition, their active triptycene cups fused at the central porphyrin core render possible potential application in host-guest chemistry.