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Transparent and colorless solar cells are attractive new photovoltaic devices as they could bring new opportunities to harness sunlight energy and particularly for their integration in windows. In this work, a new zinc phthalocyanine was synthesized and investigated as sensitizer in dye-sensitized solar cell (DSSC) for this purpose. The zinc phthalocyanine features a benzoic acid anchoring group and six thio(4-tertbutylphenyl) substituents in ${\alpha }$ position of the phtalocyanine. The dye was characterized by absorption and emission spectroscopy and by electrochemistry. The physico-chemical properties show that the dye fulfills the criteria for such an application. A detailed computational study indicates that the electronic communication with $\mathrm{TiO}_{2}$ conduction is weak owing to the absence of overlapping of the wavefunctions of the dye with those of the $\mathrm{TiO}_{2}$ semiconductor. The photovoltaic performances of the zinc phthalocyanine were measured in $\mathrm{TiO}_{2}$-based DSSC that revealed inefficient electron injection, which certainly can be explained by the weak electronic coupling of the dye with $\mathrm{TiO}_{2}$ that limits electron injection efficiency. A strategy is proposed to make better-performing sensitizers.

In the context of climate change, it is of utmost importance to replace the use of fossil fuels as raw material in areas of industrial interest, for example, in the production of chemical inputs. In this context, a viable option is biomass, since by subjecting it to chemical processes such as pyrolysis, it is possible to obtain platform molecules that are the basis for the generation of value-added chemical products. Acetals are molecules obtained from biomass derivatives, which have various applications in cosmetic chemistry, in the pharmaceutical industry as intermediates or final compounds, food additives, among others. Different catalysts have been used in the acetalization reaction, including MOFs, which have the advantage of being porous materials with high surface area values. The large surface area translates into a greater number of catalytically active sites available for the reaction. Among the MOFs that have been used for this purpose is MOF-808, which is characterized by having a lower number of ligands attached to its metal cluster, therefore, it has a greater exposure of the metals that make up its structure. In this context, the work carried out studied the catalytic performance of MOF-808 when its Zr(IV) metal centers are replaced by Hf(IV) and Ce(IV) atoms in the acetalization reaction of benzaldehyde with methanol. The MOFs obtained by solvothermal synthesis were characterized by powder X-ray diffraction, N2 adsorption and desorption, FT-IR spectroscopy, acid–base potentiometric titration, XPS and thermogravimetric analysis. The results of the catalysis indicate that the MOF with the best performance was MOF-808-Ce, which achieved conversions greater than 80% in a period of ten minutes. MOF-808-Ce exhibits a higher number of defects and therefore a higher availability of catalytic sites for the reaction to occur, which explains the better performance. Finally, the performance of MOF-808 in the acetalization of benzaldehyde with methanol was also supported by density functional theory (DFT) calculations. [ABSTRACT FROM AUTHOR]

A theoretical study of the reported photocatalytic systems based on Zr-based MOF (UiO-67) with biphenyl-4,4′-dicarboxylic acid (bpdc) and 2,2′-bipyridine-5,5′-dicarboxylic acid (bpydc) as linkers was performed. Quantum chemical calculations were carried out to understand the optical properties of the materials and to facilitate the rational design of new UiO-67 derivatives with potentially improved features as photocatalysts under ambient conditions. Hence, the effect of the structural modifications on the optical properties was studied considering different designs based on the nature of the linkers: in 1 only the bpdc linker was considered, or the mixture 1 : 1 between bpdc and bpydc linkers (labeled as 1A). Also, substituents R, –NH2, and –SH, were included in the 1A MOF only over the bpdc linker (labeled as 1A-bpdc-R) and on both bpdc and bpydc linkers (labeled as 1A-R). Thus a family of six isoreticular UiO-67 derivatives was theoretically characterized using Density Functional Theory (DFT) calculations on the ground singlet (S0) and first excited states (singlet and triplet) using Time-Dependent Density Functional Theory (TD-DFT), multiconfigurational post-Hartree–Fock method via Complete Active Space Self-Consistent Field (CASSCF). In addition, the use of periodic DFT calculations suggest that the energy transfer (ET) channel between bpdc and bpydc linkers might generate more luminescence quenching of 1A when compare to 1. Besides, the results suggest that the 1A-R (R: –SH and NH2) can be used under ambient conditions; however, the ET exhibited by 1A, cannot take place in the same magnitude in these systems. These ET can favor the photocatalytic reduction of a potential metal ion, that can coordinate with the bpydc ligand, via LMCT transition. Consequently, the MOF might be photocatalytically active against molecules of interest (such as H2, N2, CO2, among others) with photo-reduced metal ions. These theoretical results serve as a useful tool to guide experimental efforts in the design of new photocatalytic MOF-based systems. [ABSTRACT FROM AUTHOR]

Four new halogen-bonded cocrystals of biological methylxanthines, named caffeine, theophylline and theobromine, have been prepared with 1,4-diiodotetrafluorobenzene as a halogen bond donor by mechanochemical and solution processes. For theophylline, N⋯I and N⋯O interactions were observed, while for caffeine and theobromine, only N⋯I was detected. The solids were characterized by PXRD, SC-XRD, FTIR and thermal methods (TGA-DSC analyses). In addition, the solid-state photoluminescence properties of the methylxanthines and their respective cocrystals have been studied and quantum chemistry calculations have been performed to rationalise and understand the electronic and optical properties of all compounds. This work provides a triad of natural methylxanthines capable of forming halogen-bonded multicomponent systems that can give rise to a cocrystal-to-crystal transformation with off–on luminescence activation. [ABSTRACT FROM AUTHOR]

The increasing CO2 emissions and their direct impact on climate change due to the greenhouse effect are environmental issues that must be solved as soon as possible. Metal–organic frameworks (MOFs) are one class of crystalline adsorbent materials that are thought to have enormous potential in CO2 capture applications. In this research, the effect of changing the metal center between Zr(IV), Ce(IV), and Hf(IV), and the linker between BDC and PDC has been fully studied. Thus, the six UiO-66 isoreticular derivatives have been synthesized and characterized by FTIR, PXRD, TGA, and N2 adsorption. We also report the BET surface area, CO2 adsorption capacities, kinetics, and the adsorption isosteric heat (Qst) of the UiO-66 derivatives mentioned family. The CO2 adsorption kinetics were evaluated using pseudo-first order, pseudo-second order, Avrami's kinetic models, and the rate-limiting step with Boyd's film diffusion, interparticle diffusion, and intraparticle diffusion models. The isosteric heats of CO2 adsorption using various MOFs are in the range 20–65 kJ mol−1 observing differences in adsorption capacities between 1.15 and 4.72 mmol g−1 at different temperatures due to the electrostatic interactions between CO2 and extra-framework metal ions. The isosteric heat of adsorption calculation in this report, which accounts for the unexpectedly high heat released from Zr-UiO-66-PDC, is finally represented as an increase in the interaction of CO2 with the PDC linker and an increase in Qst with defects. [ABSTRACT FROM AUTHOR]

Mono- and bimetallic UiO-66 nanocatalysts were synthesized using the solvothermal synthesis method and evaluated in the aldol condensation reaction of benzaldehyde and acetone in a batch reactor. N2 physisorption, thermogravimetric analysis, temperature-programmed desorption of ammonia, X-ray diffraction, field-emission scanning electron microscopy–energy-dispersive X-ray, X-ray photoelectron spectroscopy, potentiometric titration, and Fourier transform infrared were used to characterize the nanocatalysts. The higher activity exhibited by the Zr/Hf-UiO-66 catalyst could be attributed to the lower orbital energy interaction with benzaldehyde, as shown by density functional theory. A synergetic effect is observed for the bimetallic UiO-66 nanocatalyst between Zr and Hf, obtaining a higher reaction rate than the monometallic nanocatalysts. Meanwhile, this antagonistic effect was shown in the bimetallic catalysts between Zr and Ce, which was less active than the monometallic UiO-66 catalyst due to free COOH generated during the synthesis. Finally, the selectivity results showed that incorporating Hf and Ce on Zr-UiO-66 favors benzalacetone formation by cross-coupling condensation of benzaldehyde and acetone at isoconversion conditions. [ABSTRACT FROM AUTHOR]

Aluminium is the most abundant metal in the earth crust and so far, there is no evidence on an important role in the human body. However, the relation of aluminium exposure on human health and aluminium‐related diseases is well known. The aim of this review is to summarize the most recent advances on multidentate organic compounds such as naphthalene, coumarin, quinoline, Schiff bases, benzothiazole, benzimidazole, rhodamine, pyrene carbazole, and julolidine derivatives as Al3+ fluorescent sensor starting from an analytical viewpoint (sensibility, selectivity), their application in fluorescent bioimaging in vitro or/and in vivo, and photophysical mechanisms. [ABSTRACT FROM AUTHOR]

A theoretical procedure, via quantum chemical computations, to elucidate the detection principle of the turn‐off luminescence mechanism of an Eu‐based Metal‐Organic Framework sensor (Eu‐MOF) selective to aniline, is accomplished. The energy transfer channels that take place in the Eu‐MOF, as well as understanding the luminescence quenching by aniline, were investigated using the well‐known and accurate multiconfigurational ab initio methods along with sTD‐DFT. Based on multireference calculations, the sensitization pathway from the ligand (antenna) to the lanthanide was assessed in detail, that is, intersystem crossing (ISC) from the S1 to the T1 state of the ligand, with subsequent energy transfer to the 5D0 state of Eu3+. Finally, emission from the 5D0 state to the 7FJ state is clearly evidenced. Otherwise, the interaction of Eu‐MOF with aniline produces a mixture of the electronic states of both systems, where molecular orbitals on aniline now appear in the active space. Consequently, a stabilization of the T1 state of the antenna is observed, blocking the energy transfer to the 5D0 state of Eu3+, leading to a non‐emissive deactivation. Finally, in this paper, it was demonstrated that the host‐guest interactions, which are not taken frequently into account by previous reports, and the employment of high‐level theoretical approaches are imperative to raise new concepts that explain the sensing mechanism associated to chemical sensors. [ABSTRACT FROM AUTHOR]

The turn‐on luminescent chemosensor [2‐Hydroxy‐1‐naphthaldehyde‐(2‐pyridyl) hydrazone] (L), selective to Al3+ ions, was studied by means of density functional theory (DFT) and time‐dependent‐DFT quantum mechanics calculations. The UV‐Vis absorption and the radiative channel from the adiabatic S1 excited state were assessed in order to elucidate the selective sensing mechanism of L to Al3+ ions. We found that twisted intramolecular charge transfer (TICT) and photoelectron transfer (PET), which alter the emissive state, are responsible for the luminescence quenching in L. After coordination with Al3+, the TICT is blocked, and PET is no longer possible. So, the emission of the coordination complex is activated, and a fluorescence effect enhanced by chelation is observed. For compounds with Zn2+ and Cd2+, the luminescence quenching is caused by PET, while for Ni2+, ligand to metal charge transfer is the prominent mechanism. To go into more detail, the metal‐ligand interaction was analyzed via the Morokuma‐Ziegler energy decomposition scheme and the natural orbital of chemical valence. [ABSTRACT FROM AUTHOR]

In the context of climate change, it is of utmost importance to replace the use of fossil fuels as raw material in areas of industrial interest, for example, in the production of chemical inputs. In this context, a viable option is biomass, since by subjecting it to chemical processes such as pyrolysis, it is possible to obtain platform molecules that are the basis for the generation of value-added chemical products. Acetals are molecules obtained from biomass derivatives, which have various applications in cosmetic chemistry, in the pharmaceutical industry as intermediates or final compounds, food additives, among others. Different catalysts have been used in the acetalization reaction, including MOFs, which have the advantage of being porous materials with high surface area values. The large surface area translates into a greater number of catalytically active sites available for the reaction. Among the MOFs that have been used for this purpose is MOF-808, which is characterized by having a lower number of ligands attached to its metal cluster, therefore, it has a greater exposure of the metals that make up its structure. In this context, the work carried out studied the catalytic performance of MOF-808 when its Zr(IV) metal centers are replaced by Hf(IV) and Ce(IV) atoms in the acetalization reaction of benzaldehyde with methanol. The MOFs obtained by solvothermal synthesis were characterized by powder X-ray diffraction, N 2 adsorption and desorption, FT-IR spectroscopy, acid-base potentiometric titration, XPS and thermogravimetric analysis. The results of the catalysis indicate that the MOF with the best performance was MOF-808-Ce, which achieved conversions greater than 80% in a period of ten minutes. MOF-808-Ce exhibits a higher number of defects and therefore a higher availability of catalytic sites for the reaction to occur, which explains the better performance. Finally, the performance of MOF-808 in the acetalization of benzaldehyde with methanol was also supported by density functional theory (DFT) calculations.

The increasing CO 2 emissions and their direct impact on climate change due to the greenhouse effect are environmental issues that must be solved as soon as possible. Metal-organic frameworks (MOFs) are one class of crystalline adsorbent materials that are thought to have enormous potential in CO 2 capture applications. In this research, the effect of changing the metal center between Zr(IV), Ce(IV), and Hf(IV), and the linker between BDC and PDC has been fully studied. Thus, the six UiO-66 isoreticular derivatives have been synthesized and characterized by FTIR, PXRD, TGA, and N 2 adsorption. We also report the BET surface area, CO 2 adsorption capacities, kinetics, and the adsorption isosteric heat ( Q st ) of the UiO-66 derivatives mentioned family. The CO 2 adsorption kinetics were evaluated using pseudo-first order, pseudo-second order, Avrami's kinetic models, and the rate-limiting step with Boyd's film diffusion, interparticle diffusion, and intraparticle diffusion models. The isosteric heats of CO 2 adsorption using various MOFs are in the range 20-65 kJ mol -1 observing differences in adsorption capacities between 1.15 and 4.72 mmol g -1 at different temperatures due to the electrostatic interactions between CO 2 and extra-framework metal ions. The isosteric heat of adsorption calculation in this report, which accounts for the unexpectedly high heat released from Zr-UiO-66-PDC, is finally represented as an increase in the interaction of CO 2 with the PDC linker and an increase in Q st with defects.

The optical properties and transduction mechanisms in three reported optical chemosensors based on crown ether with selectivity turn-on luminescence toward Na + over K + , were investigated using Density Functional Theory/Time-Dependent Density Functional Theory (DFT/TD-DFT). The analysis of the structural stability of the conformers enables us to understand the optical properties of the sensors and their selectivity toward Na + . The UV-Vis absorption and the radiative channels of the adiabatic S 1 excited state were assessed. In these reported sensors, the Photoinduced Electron Transfer (PET) from the nitrogen and the oxygen (O-atoms of the substituted N-phenylaza group) lone pairs to fluorophore groups lead to a nonradiative deactivation process in the fluorophore to p-conjugated anilino-1,2,3-triazol ionophore. This Intramolecular Charge Transfer (ICT) deactivation produced the luminescence quenching in the free sensors and K + /C1 complexes. The Na + /sensor interaction produced a Chelation Enhanced Fluorescence (CHEF) due to the inhibition of the PET and ICT, which was confirmed via the calculated oscillator strength of the emission process. The K + /sensor interaction displayed the possibility of PET in C3; however, this fact was inconclusive to affirm the quenching of luminescence, the CHEF in C2 and C3 and the selectivity toward Na + over K + in these systems. For this reason, simulation of the absorption and emissions spectra (calculated oscillator strength), calculation of the kinetic parameters (in charge transfers and radiative deactivations process), analysis of the metal-ligand interaction character, and the analysis of the structural stability of the conformers were determinant factors to understand the selectivity and the optical properties of these chemosensors. The results suggest that these theoretical tools can also be used to predict the optical properties and Na + /K + selectivity of optical chemosensors., (© 2022 Wiley-VCH GmbH.)

We report the synthesis and theoretical study of two new colorimetric chemosensors with special selectivity and sensitivity to Ni 2+ and Cu 2+ ions over other metal cations in the CH 3 CN/H 2 O solution. Compounds ( E )-4-((2-nitrophenyl)diazenyl)- N , N -bis(pyridin-2-ylmethyl)aniline (A) and ( E )-4-((3-nitrophenyl)diazenyl)- N , N -bis(pyridin-2-ylmethyl)aniline (B) exhibited a drastic color change from yellow to colorless, which allows the detection of the mentioned metal cations through different techniques. The interaction of sensors with these metal ions induced a new absorption band with a hypsochromic shift to the characteristic signal of the free sensors. A theoretical study via time-dependent density functional theory (TD-DFT) was performed. This method has enabled us to reproduce the hypsochromic shift in the maximum UV-vis absorption band and explain the selective sensing of the ions. For all of the systems studied, the absorption band is characterized by a π → π* transition centered in the ligand. Instead of Ni 2+ and Cu 2+ ions, the transition is set toward the σ* molecular orbital with a strong contribution of the 3d x 2 - y 2 transition (π → 3d x 2 - y 2 ). These absorptions imply a ligand-to-metal charge transfer (LMCT) mechanism that results in the hypsochromic shift in the absorption band of these systems.

A methodology that allows us to explain the experimental behavior of a turn-on luminescent chemosensor is proposed and verified in 1-[(1 H -1,2,4-triazole-3-ylimino)-methyl]-naphthalene-2-ol] (L1), selective to Al 3+ cations. This sensor increases its emission when interacting with ions upon excitation at 442 nm, which is denoted as the chelation-enhanced fluorescence effect. Photoinduced electron transfer is responsible for the fluorescence quenching in L1 at 335 nm, in Ni 2+ /L1 at 385 nm, and in Zn 2+ /L1 at 378 nm. In Ni 2+ /L, ligand-to-metal charge transfer (LMCT), from the molecular orbital of the ligand to the Ni 3d x 2  -  y 2 orbital, can contribute to the quenching of fluorescence. Based on oscillator strength, the highest luminescence intensity of L1 at 401 nm and that of Al 3+ /L1 at 494 nm in relation to the others is evidenced. The consideration of the relative energies of the excited states and the calculation of the rate and lifetime of the electron transfer deactivation are necessary to get a good description of the sensor.