Bridging Oxygen Atoms Research Articles

Viscosity, Free Activation Energy, and Glass Transition Temperature of Potassium Boron K2O–B2O3 Melts

The viscosity of potassium–boron melts is measured in the temperature range 918–1699 K using a vibrational viscosimeter. The content of potassium oxide is varied from 0.74 to 28.46 mol %. The parameters of the viscous flow in melts (the configuration–activation energy(εh) and the shifting energy of the bridging oxygen atoms’ bonds (U∞)) using the configuration–activation model are calculated for two temperature intervals 918–1400 K and 1400–1699 K. The glass transition temperature (Tg) is measured by differential scanning calorimetry (DSC) and the concentration dependence of the glass transition temperature on the content of potassium oxide in the melt is shown.

Iminophenol as a ligand or cation in cobalt(II and II,III) complexes: synthetic approaches, spectral and structural studies

New complexes [H2L]2CoCl4 (І) and [CoІІCоІІІCl2L3]H2O (ІІ), where HL is a condensation product of o-vanillin and methylamine, were synthesized and characterized by IR, UV/Vis spectroscopies, and X-ray structural analysis. For the synthesis of I, cobalt (II) chloride was used as a metal source, while for II, cobalt powder and its salt were used simultaneously. In the preparation of I, the use of methylamine hydrochloride contributed to the formation of tetrachlorocobaltate(II) with the protonated Schiff base H2L+as a cation. The monovalent cations are almost planar and show the presence of intramolecular O/N–HО hydrogen bonds. In the crystal, columns of cations connected by - stacking alternate with double-row columns of tetrahedral [CoCl4]2– anions and are additionally joined by a branched system of O/N–HCl hydrogen bonds. Crystal II is built of neutral molecules CoІІСоІІІCl2L3 and uncoordinated water molecules. In the molecule, the main CoІІІL3 fragment with a metal atom in the octahedral environment of three deprotonated ligands attaches a cobalt(II) atom at the CoIICoIII distance of 3.17 Å. The cobalt(II) atom has a highly distorted five-coordinate СоІІО3Cl2 environment formed by two bridging oxygen atoms of deprotonated phenoxy groups, the O atom of the methoxy group of the ligands, and two chlorine atoms. The obtained results allow us to propose the use of the metal salt+its powder combination for the purposeful synthesis of mixed-valent complexes of metals capable of exhibiting various oxidation states. Deliberate protonation of the Schiff base can be used to prepare organic-inorganic metal halide hybrids with functionalized cations.

Structure of amorphous materials in the NASICON system NaTi2Si x PO12

The structure of glasses in the sodium (Na) super-ionic conductor (NASICON) system NaTi2Si x PO12 with x = 0.8 and x = 1.0 was explored by combining neutron and high-energy x-ray diffraction with 29Si, 31P and 23Na solid-state nuclear magnetic resonance (NMR) spectroscopy. The 29Si magic angle spinning (MAS) NMR spectra reveal that the silica component remains fully polymerized in the form of Si4 units, i.e. the silicon atoms are bound to four bridging oxygen atoms. The 31P{23Na} rotational echo adiabatic passage double resonance (REAPDOR) NMR data suggest that the 31P MAS NMR line shape originates from four-coordinated P n units, where n = 1, 2 or 3 is the number of bridging oxygen atoms per phosphorus atom. These sites differ in their 31P-23Na dipolar coupling strengths. The results support an intermediate range order scenario of a phosphosilicate mixed network-former glass in which the phosphate groups selectively attract the Na+ modifier ions. Titanium takes a sub-octahedral coordination environment with a mean Ti–O coordination number of 5.17(4) for x = 0.8 and 4.86(4) for x = 1.0. A mismatch between the P–O and Si–O bond lengths of 8% is likely to inhibit the incorporation of silicon into the phosphorus sites of the NASICON crystal structure.

Interaction of Atomic Deuterium with Rutile TiO2(011)-(2×1)

Inspired by the significance of hydrogen–solid interaction in hydrogen energy and catalysis, adsorption, diffusion, and desorption behaviors of deuterium atoms in rutile TiO2(011) have been investigated by temperature-programmed desorption (TPD) and ultraviolet photoelectron spectroscopy (UPS). Upon exposure, a small portion of D atoms adsorb at surface oxygen sites, resulting in the band gap states at 1.35 eV below the Fermi level and desorbing as water at ∼400 K. Most of the D atoms will diffuse into the bulk due to the relatively low activation barrier and the huge capacity of the solid material. These bulk D species desorb as D2/HD between 500 and 800 K. While the desorbing D2O from surface hydroxyls saturates at ∼0.10 monolayer (ML), the yielding D2 is about 96 ML (equivalent coverage) at the largest atomic D exposure of 4.54 langmuir and no saturation trend has been observed in the present work. Detailed analysis indicates the bulk D will diffuse back to the surface and recombine as D2 at elevated temperatures. The differences between the behavior of H(D) in rutile TiO2(110) and TiO2(011) have been discussed by considering the presence of additional bridging oxygen atoms between the in-plane and topmost ones on the latter surface. The striking finding that most surface D atoms diffuse into the bulk of rutile TiO2(011) will not only broaden our understanding of the interaction of H/D with the prototypical metal oxide material but also provide clues to investigate the mechanism of H/D involving reactions over TiO2 catalysts, for example, hydrogen evolution and hydrogenation.

Synthesis, structure, and catalytic activity of polyoxometalate (C7H15N4)2[Co(H2O)6][C6H12N2CoMo6O24]·4H2O in the azide–alkyne cycloaddition reaction

A new polyoxomolybdate with a formula of (C7H15N4)2 [Co(H2O)6] [C6H12N2CoMo6O24]·4H2O (1) was synthesized and then it was characterized using IR, EDX and X-ray crystallography. The unit cell of 1 consists of two [Co(H2O)6]2+ and one N-methyluroptropine (C7H15N4)+ cations, and one polyanion [C6H12N2CoMo6O24]4- and four lattice water molecules. In the polyanion [C6H12N2CoMo6O24]4-, molybdenum metals are surrounded by two terminal and one bridging oxygen atoms and also one oxygen of the trimethanolamine ligand is coordinated to each Mo metal. Cobalt metal in the center of the polyanion is also bonded to four bridged oxygen atoms and two oxygen atoms of the trimethanolamine ligand. This novel polyoxomolybdate was used as an efficient catalyst for the azide–alkyne cycloaddition reaction to produce various 1,2,3-triazoles in high yields (34–99%).

A combined experimental and theoretical study of covalent vs noncovalent dimer formation in vanadium(V) complexes with Schiff base ligands

This manuscript reports the synthesis, spectroscopic and X-ray characterization of three new vanadium(V) complexes, namely [VO2L1] (1), (μ-O)2[V(O)(L2)2]·2CH3CN (2) and (μ-O)2[V(O)(L3)2]·CH3CN (3) [HL1 (2-ethoxy-6-((quinolin-8-ylimino)methyl)phenol), HL2 (2-(1-(2-(methylamino)ethylimino)propyl)phenol) and HL3 (2-(1-(2-(ethylamino)ethylimino)propyl)phenol)]. Complex 1 is a mononuclear dioxovanadium(V) system containing a five coordinated metal center, whilst complexes 2 and 3 are centrosymmetric dinuclear systems with two [(L)V = O] moieties [(L2)- for 2 and (L3)- for 3], which are linked together through asymmetrically bridging oxygen atoms. DFT calculations have been used to rationalize the different behavior of complex 1, that is related to the lack of strong H-bond donors and strong ability to self-assemble via electrostatically enhanced π-stacking interactions. Moreover, the strength of π–π and CH–π interactions has been evaluated and the interactions have been characterized by several computational tools like MEP, QTAIM and NCI Plot.

Theoretical insight on the importance of CH···O and NH···O interactions in the crystal packing of a decavanadate synthesized from a simple V(IV) precursor

In this manuscript, the synthesis and X-ray characterization of a new decavanadate complex, [H2L1]2[HL2]2[V10O28], is reported, where [H2L1] and [HL2] are the protonated forms of ligands L1 and L2 [L1 = 4-(2-aminoethyl)morpholine and L2 = N-ethylidene-2-morpholinoethanamine]. H-bonding interactions between the bridging oxygen atoms of the anion and the ammonium groups (N+–H···O) of the ligands are selectively formed. Moreover, a multitude of CH···O interactions are also established between the counter ions. DFT calculations have been used to rationalize the interactions observed in the solid state and to compare the relative importance of the charge assisted NH···O H-bonds with the CH···O ones, evidencing that almost 40 % of the interaction energies are due to CH···O contacts. Moreover, using MEP surface calculations, the H-bond acceptor ability of the different O-atoms of [V10O28]6- anion has been studied. To our knowledge, such analysis is unprecedented in the literature.

Molecular Insights on the Adsorption of Polycyclic Aromatic Hydrocarbons on Soil Clay Minerals

The role of soil clay minerals is often ignored in studying the polycyclic aromatic hydrocarbons (PAHs) adsorption in soil. In this work, Monte Carlo and molecular dynamics simulations are used to study the adsorption of PAHs on several typical soil clay mineral surfaces, such as (0 0 1) and (0 0 − 1) of kaolinite, pyrophyllite, mica, and montmorillonite. Results show that van der Waals and cation-π interactions dominate the interactions between PAHs and mineral surfaces. Bridging oxygen atom on the mineral surface structure is the main site of hydrophobic interaction with PAHs. The cation-π effect can significantly enhance the PAHs adsorption energy. In addition, the adsorption on clay minerals is enhanced with the increase in the number of PAHs aromatic rings. In the presence of water, different minerals exhibit different adsorption properties. A layer of water molecules is formed close to the kaolinite (0 0 1) surface, reducing PAHs adsorption. The self-diffusion coefficient (D) of PAHs in Ca2+-montmorillonite is more significant than that in K+-mica, due to the different hydration properties of mineral cations. These findings reveal the adsorption mechanism of PAHs on the surfaces of typical clay minerals at a molecular scale and provide a new perspective for soil adsorption of PAHs.

First principles study of structural and electron properties in scorodite: the bulk and surface.

Scorodite (FeAsO4·2H2O) is an ideal material for the fixation of arsenic that has attracted considerable research interest in recent decades. However, the position of the H atom in the scorodite crystal structure, water molecular configuration, surface morphology, and chemical state of the surface atoms have not been reported. In this work, density functional theory (DFT) is used to optimize the scorodite crystal structure, and the atomic bonding is analyzed. At the same time, a surface model is constructed to calculate the configuration and electronic structure of the surface atoms for different coordination groups. The results show that the tetrahedral [AsO4] and octahedral [FeO4(2H2O)] groups in the scorodite crystal structure have good stability(geometry configuration), and the covalent bond strength between the As atom and the bridged oxygen atom (Ob) is greater than that between the Ob atom and the Fe atom. The water molecules in the crystal structure do not seriously deform and ionize. The configuration of the water molecules remains stable through electrostatic interactions (Ow-Fe) and hydrogen bonding (H-Ob). The Fe atoms on the surface of scorodite can coordinate with OH and H2O, while the As atoms can only form a stable coordination with OH. When an Fe atom on the surface coordinates with two H2O atoms, the Fe atom will shrink to the inside of the bulk. With the increase in the hydroxylation number of the Fe atom, the bonding strength between the Fe atom and the Ob atom decreases. Different surface configurations do not affect the stability(geometry configuration) of the [AsO4] structure. In addition, the surface water molecular layer has a very weak effect on the surface coordination configuration. By contrast, in the surface configuration of the (W + OH) structure, the change in the surface atomic layer spacing is the smallest.

Twisted [C2O5]2--groups in Ba[C2O5] pyrocarbonate.

The inorganic pyrocarbonate salt Ba[C2O5] contains twisted pyrocarbonate anions ([C2O5]2-), an atomic arrangement previously not observed in other pyrocarbonates. This unexpected additional structural degree of freedom points towards an enlarged chemical variability in this novel group of compounds. Ba[C2O5] was synthesized in a laser-heated diamond anvil cell at 30(2) GPa by heating a mixture of Ba[CO3] + CO2 to ≈ 1500(200) K. Its crystal structure was solved from single crystal synchrotron X-ray diffraction data and confirmed by density functional theory-based calculations. The two planar [CO3]2--groups of the [C2O5]2--anion are strongly twisted around the bridging oxygen atom. Ba[C2O5] has been observed in the pressure range of 5-30 GPa, where its symmetry is P6/m with Z = 12.

Rapid wet chemical synthesis of bioactive glass with high yield by probe sonication.

Bioactive glasses (BGs) are inorganic biomaterials which possess favourable properties for bone repair and regeneration. The biological properties of the BGs depend on their physical features. This manuscript describes a simple methodology for rapid synthesis of BG nanoparticles (NPs) with tailored physical properties using ultrasonic disruption produced by an ultrasonic probe. The ultrasonic probe generates stable and transient cavitation which increases the mass transfer and accelerates the chemical reaction. This approach is relatively green as it evades the use of the drastic acidic conditions required for hydrolysis. The prepared BG NPs were characterized by Fourier transform infra-red (FTIR) spectroscopy, Raman spectroscopy, scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy (TEM), X-ray diffraction (XRD), particle size analysis (PSA), nitrogen adsorption/desorption and BET surface area analysis, X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectrometry (ICP-OES), and in situ high temperature synchrotron XRD. The effects of ultrasonic irradiation time, and amplitude on the surface properties were investigated and the results confirmed that both parameters, especially amplitude, have significant effects on the physical properties of the prepared BG NPs. The XPS results showed that both, amplitude and time have a pronounced effect on the bridging and non-bridging oxygen atoms bonded to the Si centre in the BG samples, which play an important role in the bioactivity of the BG NPs. The in situ high temperature XRD patterns indicated a gradual phase transformation for the BG samples synthesized at different ultrasonic irradiation times and amplitudes. The TEM images showed that uniform nano-sized BG particles were obtained at 50% amplitude in only 10 minutes. A bimodal particle size distribution was observed with an increasing reaction time, up to 30 minutes, due to an increase in the formation of vortices at the interface where nucleation starts. All the prepared samples exhibited a glassy structure with the composition 70SiO2 : 25CaO : 5P2O5 and were highly bioactive. The proposed method would give a quick route for the synthesis of bioactive glasses and other ceramics with controlled physical properties.

Complex Optical Investigation of Sodium Superoxide Loaded Phosphovanadate Glass System in Ultra-Violet and Visible Region

Sodium superoxide loaded phosphovanadate based glass systems were prepared from a mixture of vanadium pentoxide (V2O5), phosphorus pentoxide (P2O5) boric acid (H3BO3) and sodium superoxide (NaO2) using a melt-quenching method. Amorphous phase of as-prepared glass system confirmed using XRD technique. Surface morphology of glass system studied using scanning electron microscope. Ultraviolet-visible spectroscopy was employed to extract complex optical parameters like direct and indirect optical band gap, Urbach energy, refractive index, complex dielectric constant and optical conductivity. The absorption bands in the region 200 - 400 nm are recognized to the ligand-to-metal charge transfer. The region of 400 - 600 nm is ascribed to the pair excitation processes. The refractive index increases initially and then decreases for 15 and 20 mol % of NaO2 due non bridging oxygen (NBO) atoms. The 25 mol % of NaO2 sample shows maximum value of extinction coefficient and refractive index. The direct and indirect band gap energies vary in between 2.067 to 1.824 eV and 1.869 to 1.495 eV, respectively. With increase in concentration of NaO2, the effective band gap of NaO2 decreases because band edge shifted into forbidden gap due to increase in defect levels below the conduction. This primary report on sodium superoxide loaded phosphovanadate based glass systems opens wide avenue for battery and supercapacitor applications. Tailing in the bandgap was observed and found to obey Urbach rule. HIGHLIGHTS Sodium superoxide-phosphovanadate glass system prepared by melt-quenching method Complex optical properties of prepared glass system studied successfully Glass system have characteristics of trapping of light Also, glass system has ability to slow down light GRAPHICAL ABSTRACT

Sodium Aminodiboranates Na(H3BNR2BH3): Structural and Spectroscopic Studies of Steric and Electronic Substituent Effects

We describe the syntheses of a series of sodium aminodiboranate salts, Na(H3B-NR2-BH3), with different substituents on nitrogen, including sodium salts of the unsubstituted aminodiboranate, H3B-NH2-BH3-, and of the N-substituted anions H3B-NRR'-BH3-, where NRR' = NHMe, NHEt, NH(SiMe3), NEt2, N(i-Pr)2, N(SiMe3)2, NMe(i-Pr), NMe(t-Bu), NMe(SiMe3), and the pyrrolidide and piperidide derivatives NC4H8, NC5H10, and NC5H8-cis-2,6-Me2. The compounds have been characterized by 1H and 11B NMR spectroscopy and IR spectroscopy; crystallographic studies have been carried out for the unsolvated N,N-dimethylaminodiboranate salt Na(H3B-NMe2-BH3) and several sodium aminodiboranate salts in which the sodium ions are solvated with ethers (dioxane, diglyme, tetrahydrofuran, and 12-crown-4) or amines (N,N,N',N'-tetramethylethylenediamine). One of the structures contains a rare example of an ether ligand in which one oxygen atom bridges between two metal ions. General structural and spectroscopic trends as a function of the substituents on nitrogen are discussed.

Investigation of the thermal shrink mechanism, thermal conductivity and compressive resistance of TaTiP3O12 ceramics

Dense TaTiP3O12 ceramics were synthesized by the solid-state method and spark plasma sintering (SPS) with 6 wt% V2O5 as a sintering aid, and their phase, microstructure, thermal conductivity, hardness, compressive strength, and expansion property and mechanism were investigated. Results show that the pure phase can be achieved by the two methods. In particular, the sample prepared by SPS possesses a relative density of 97.62% and a porosity of 3.07%, and has better properties than that prepared by the solid-state method. The SPS sample has a thermal conductivity at room temperature of 2.03 w/(m· °C), a Vickers hardness of 4.34 GPa and a compressive strength of 175.98 MPa, which are 0.95, 1.49 and 1.59 times greater than those of the sample prepared by the solid-state method, respectively. In addition, the TaTiP3O12 ceramic prepared by SPS exhibits a linear ultralow negative thermal expansion property with a coefficient of thermal expansion of −0.74 × 10−6 °C −1 (-100–400 °C). The negative thermal expansion in TaTiP3O12 is induced by the coupling effect of [Ta(Ti)O6] octahedron and [PO4] tetrahedron caused by the transverse vibration of bridging oxygen atoms.

Vibrational characteristics of aluminum–phosphate compounds by an experimental and theoretical approach

Aluminum phosphates are materials with relatively wide potential applications in many industries. The vibrational features of selected compounds were established on Raman and infrared spectroscopy. The experimentally determined spectra are compared to those calculated by ab initio methods. This gives a unique possibility of a proper assignment of the experimental spectral features to specific modes of vibration. In the results, it was evidenced that the spectra are characterized by two specific intense bands in the mid- and high-frequency range due to the P–O–P and P–O bonds in [PO4] tetrahedron vibrations. The position of the high-frequency band is related to the number of bridging oxygen atoms connecting [PO4] tetrahedrons in the unit cell. Additionally, the differences in the spectra were evidenced as a result of different polymorphic forms of the selected compounds. Therefore, the results may be useful in determining the phase composition of polyphase materials or structural features of aluminum–phosphate glasses and glass–ceramic materials.

Enhancements of Second Harmonic Generation and Birefringence in Traditional RbTiOPO4‐Type Crystals by Aliovalent Substitution of Ti Site

AbstractStrong second harmonic response and large birefringence of nonlinear optical (NLO) materials have important scientific and technical significance for tunable lasers. The second harmonic generation (SHG) response in NLO crystals has been generally enhanced by improving the polarization of bridged oxygen atoms or local structural distortions, while the synergy of the two contributions to enhance the SHG response is rarely explored. To this end, new crystals with traditional RbTiOPO4 (RTP)‐structure, Rb1–xTi1–xSbxOPO4 (x = 0.01, 0.03, and 0.06), containing novel functional SbO6 octahedra and Rb vacancies are designed through a one‐site aliovalent substitution and grown in this work. Rb0.94Ti0.94Sb0.06OPO4 exhibits an enhanced SHG response, nearly 1.48 times that of the RTP crystal, accompanied by the largest birefringence in phosphates (exp. 0.202 at 546 nm, cal. 0.156 at 1064 nm). Theoretical calculations and crystal structure analysis confirm that the higher polarizability of bridged oxygen and the local structural distortions in Rb1–xTi1–xSbxOPO4 strengthen the NLO activity of neighboring units, thus significantly prompt the SHG effect and optical anisotropy. This study provides a new paradigm to deeply improve the NLO performance of crystal materials and benefits for expanding their practical applications.

Utilization of diamagnetic Zn(II) ion to boost the anisotropic nature of Ln(III) ion in heterodinuclear Zn(II)–Ln(III) single‐molecule magnets

A series of dimetallic ZnII–LnIII compounds of general formulae [LnZn(L)3(NO3)2]·2CH3OH (LnIII = DyIII (1), TbIII (2), GdIII(3)) was prepared by stepwise reaction of compartmental ligand LH = ((E)‐2‐((pyridin‐2‐ylmethylene)amino)phenol) with Ln (NO3)3·xH2O and Zn (NO3)2·xH2O in the presence of triethylamine as base. The single crystal XRD analysis indicated that both metallic ions are connected to each other through phenolic oxygen atom from fully deprotonated ligand. Based on the SHAPE analysis, the DyIII ion has nine coordination numbers with distorted spherical capped square antiprism geometry, while the ZnII ion has six coordination numbers with distorted octahedral geometry. DC magnetic studies reveal the existence of antiferromagnetic interaction between the ZnII and LnIII metal centers. AC magnetic studies reveal that the complex 1 show field‐induced single‐molecule magnet (SMM) properties with an effective energy barrier of 155 K under an applied dc field of 0.1 T, whereas complex 2 does not show SMM behavior. Furthermore, we conducted DFT and ab initio CASSCF + RASSI‐SO calculations to probe the single‐ion properties of Ln(III) ions and to understand the role of the diamagnetic ZnII ion in the magnetization relaxation in order to interpret the experimental observations. Ab initio calculations predict that the gz values are strongly axial in nature in the ground state of Dy(III) ion in complex 1 and that allows the magnetic relaxation to occur via excited states with a Ucal of 380.8 K. DFT calculations discovered that the presence of the diamagnetic Zn(II) ion causes greater negative charges on the bridging oxygen atoms, which enhances the anisotropy of Dy(III) ion and thus reduces the quantum tunneling of magnetization (QTM) effects, and helps to achieve better SMM features for 1.

Multiple strongly coupled antiferromagnetic spin S = 1/2 dimers in liroconite Cu2Al(As,P)O4(OH)4·4H2O

Abstract We report on the magneto-structural properties of the rare copper aluminum hydroxo-arsenate mineral liroconite with chemical composition Cu2AlAs1−x P x O4(OH)4·4H2O (x ≈ 0.2). In order to characterize the natural mineral sample chemical analyses, X-ray single crystal and powder diffraction, heat capacity and crystal water desorption, anisotropic thermal expansion and Raman scattering and magnetic susceptibility investigations have been carried out. The magnetic properties are well described by two discrete oxygen bridged Cu2+ spin S = 1/2 dimers with antiferromagnetic spin exchange ranging between −320 K and −136 K, depending on to which group-15 five-valent cation, As5+ or P5+, the dimer bridging oxygen atoms coordinate to. Accordingly the temperature dependence of the magnetic susceptibilities can be well fitted to a sum of two Bleaney–Bowers type spin S = 1/2 dimer susceptibilities suggesting that the dimers show negligible mixed coordination to (AsO4)3−/(PO4)3− tetrahedra. DFT + U calculation confirm the ratio of the spin exchange parameters of the (AsO4)3− or (PO4)3− coordinated Cu2+ – Cu2+ dimers. Inter dimer spin exchange is about two orders of magnitude smaller than intra dimer exchange.

Synthesis, X-ray crystal structure of Cu(II) 1D coordination Polymer: In View of Hirshfeld surface, FMO, Molecular electrostatic potential (MEP) and Natural Bond orbital (NBO) analyses

A dynamic area in the realm of contemporary scientific research is the synthesis of molecular systems that exhibit binding abilities for the creation of effective coordination polymeric structures. In addition to the varied network architecture, the rational design and synthesis of metal-organic coordination polymers is currently of great interest because these extended polymeric systems are vital to numerous fields of modern research. In this present research, a new 1D coordination polymer of Cu(II) complex [Cu2(mPzA)2(Bz)]n (1) has been synthesized using two different ligands i.e. 5-methyl-pyrazole-3-carboxylic acid (mPzA) and benzoic acid (Bz). X-ray crystallography study reveals that in the solid-state structure of the title complex, Cu(II) exhibits distorted trigonal bipyramidal geometry. Quantum chemical calculations using density functional theory (DFT) method have been carried out for the complex 1. The computed results further support the experimental findings of the complex adopting a square pyramidal geometry. In the basal plane, the copper atom is bonded through two nitrogen atoms and two oxygen atoms which are bridged between two copper atoms. The axial position is occupied by the oxygen atom of a carboxyl group. Frontier molecular orbital analysis using the global reactivity parameters demonstrates the compound to be stable and less reactive. Moreover, molecular electrostatic potential (MEP) is evaluated using the electron density of the compound to predict the reactive sites. The MEP map clearly indicates strong electrophonic reaction potential of this complex. Natural bond orbital (NBO) analysis has been performed to check the hyperconjugation and thereby stability of the complex 1. NBO analysis revealed the charge delocalization from the bridging oxygen atoms towards copper atoms. The Hirshfeld surface analysis demonstrates absence of π…πstacking interaction and significant contribution of H···H (39.7%) and O···H (24.1%) interactions in building the supramolecular crystal packing.

Effect of direct linkage of pyrazole carboxylic acid acceptor/anchoring group on the photovoltaic performance for phthalocyanine-sensitized solar cells

An unsymmetrical zinc phthalocyanine dye (PCA-ZnPc-4) containing six electron donating hexylsulfanyl groups and a pyrazole-3-carboxylic acid anchoring group which is directly linked to the macrocycle was synthesized to evaluate the photophysical, electrochemical, and theoretical characteristics as well as photovoltaic properties. Previously studied dye PCA-ZnPc-2, which contains the same electron donating groups and pyrazole-3-carboxylic acid anchoring group with the bridging oxygen atom, was used as a reference dye. The optimized dye-sensitized solar cell (DSSC) based on PCA-ZnPc-4 exhibited an impressive power conversion efficiency of 2.52% (JSC = 6.53 mA cm−2, VOC = 0.584 V, FF = 0.66), exceeding that of the DSSC based on PCA-ZnPc-2 (1.86%) under the same conditions. The better photovoltaic performance of PCA-ZnPc-4 is mainly due to its conjugated anchoring group, leading to efficient electron injection. This work demonstrates that the anchoring groups attached to the macrocycle without oxygen linker may enhance the photovoltaic performance of the phthalocyanine-sensitized solar cells.