MCD spectroscopy and TD-DFT calculations of magnesium tetra-(15-crown-5-oxanthreno)-phthalocyanine

An analysis of the MCD spectroscopy and TD-DFT calculations of magnesium tetra-(15-crown-5-oxanthreno)-phthalocyanine is reported. This study provides a reassessment of an earlier study on the nature of the bands in UV-visible absorption spectra of magnesium and zinc tetra-(15-crown-5-oxanthreno)-phthalocyanine that was based on an analysis of TD-DFT calculations for a series of model complexes with the B3LYP functional. A detailed analysis of MCD spectral data and TD-DFT calculations with the CAM-B3LYP functional for the complete Mg(II) complex provides an additional insight into the optical properties and electronic structures of tetra-(15-crown-5-oxanthreno)-phthalocyanines. Thus, the bands in the Q-band region are reassigned as being due exclusively to the Q transition of Gouterman’s 4-orbital model, since intense pseudo-A11 terms are observed in the MCD spectrum in a spectral region that had previously been assigned as charge transfer bands

Electronic structure and NH-tautomerism of a novel metal-free phenanthroline-annelated phthalocyanine

A novel low-symmetry A3B-type phthalocyanine annelated with a pyrazino[2,3-f]phenanthroline ring system and substituted with six solubilizing diisopropylphenoxy-groups (1) was synthesized by metalfree DBU-promoted cross-condensation of diiminoisoindolines derived from 4,5- bis(diisopropylphenoxy)phthalonitrile and pyrazino[2,3-f][1,10]phenanthroline-2,3-dicarbonitrile. The use of these particular precursors affords A3B phthalocyanine in 15% yield, while cross-condensation of the corresponding dinitriles yields only trace amounts of the target compound. Comparative studies of the A3B-type phthalocyanine and its symmetrical octa(diisopropylphenoxy)-substituted counterpart 2 reveal striking differences in the Q band regions of their UVevisible absorption (UVeVis) spectra, which could be readily rationalized through a comparison with calculated TD-DFT spectra. Since 1 can have two NH-tautomers with equivalent and non-equivalent NH-groups, and DFT calculations predict that the former tautomer is only 2.3 kcal/mol more stable than the latter one, a comprehensive analysis of 13C NMR spectra was carried out through the application of 1 He13C HMBC and HSQC techniques. It demonstrated that only the tautomer with equivalent NH-groups is present in solution

Methodological Survey of Simplified TD-DFT Methods for Fast and Accurate Interpretation of UV−Vis−NIR Spectra of Phthalocyanines

A methodological survey of density functional theory (DFT) methods for the prediction of UV−visible (vis)−near-infrared (NIR) spectra of phthalocyanines is reported. Four methods, namely, full time-dependent (TD)-DFT and its Tamm−Dancoff approximation (TDA), together with their simplified modifications (sTD-DFT and sTDA, respectively), were tested by using the examples of unsubstituted and alkoxy-substituted metal-free ligands and zinc complexes. The theoretical results were compared with experimental data derived from UV−visible absorption and magnetic circular dichroism spectroscopy. Seven popular exchange-correlation functionals (BP86, B3LYP, TPSSh, M06, CAM-B3LYP, LC-BLYP, and ωB97X) were tested within these four approaches starting at a relatively modest level using 6-31G(d) basis sets and gas-phase BP86/def2-SVP optimized geometries. A gradual augmentation of the computational levels was used to identify the influence of starting geometry, solvation effects, and basis sets on the results of TD-DFT and sTD-DFT calculations. It was found that although these factors do influence the predicted energies of the vertical excitations, they do not affect the trends predicted in the spectral properties across series of structurally related substituted free bases and metallophthalocyanines. The best accuracy for the gas-phase vertical excitations was observed in the lower-energy Q-band region for calculations that made use of range-separated hybrids for both full and simplified TD-DFT approaches. The CAMB3LYP functional provided particularly accurate results in the context of the sTD-DFT approach. The description of the higherenergy B-band region is considerably less accurate, and this demonstrates the need for further advances in the accuracy of theoretical calculations. Together with a general increase in accuracy, the application of simplified TD-DFT methods affords a 2−3 orders of magnitude speedup of the calculations in comparison to the full TD-DFT approach. It is anticipated that this approach will be widely used on desktop computers during the interpretation of UV−vis−NIR spectra of phthalocyanines and related macrocycles in the years ahead

Layers of active carbon with grafted sodium and potassium glycinate derivatives on the surface of PVC film

Porous layers from active carbon with macro-molecular cyclic amines with sodium or potassium acetate substituents were synthesized. Layers sewn to the surface of a film of PVC. It is shown that the graft zones around carbon particles consist of luminophore groupings in the form of conjugated rings, including radicals with substituted amino groups, conjugated carbon groups and oxygen atoms binding these groups. The electronic conductivity of the layers and their sorption capacity for the absorption of benzene vapor are measured. It is established that the conductivity of the layer is the higher, the smaller the PVC derivatives, the carbon particles are combined. The conductivity of the layers with potassium ions is greater than that of sodium ions. It is assumed that most of the vapors are concentrated in the pores in the carbon. The sorption capacity of layers with sodium ions is greater than that of potassium ions

Optical limiters with improved performance based on nanoconjugates of thiol substituted phthalocyanine with CdSe quantum dots and Ag nanoparticles

Two alternative synthetic approaches affording a low-symmetry A3B-type phthalocyanine 1 bearing two [2′-(2′′-mercaptoethoxy)ethoxy] anchoring substituents were developed. Due to the presence of thiol groups, this phthalocyanine could be conjugated with TOPO-capped (TOPO - trioctylphosphine)-capped CdSe quantum dots (CdSe-QDs) or oleylamine capped silver nanoparticles (Ag-NPs). The nonlinear optical behaviour of starting phthalocyanine, quantum dots, nanoparticles and their conjugates was studied by using an open aperture Z-scan technique, revealing that the grafting of 1 onto the nanomaterials resulted in a significant enhancement of the optical limiting of 1-Ag and 1-CdSe in comparison with the individual components. The conjugate 1-CdSe, being the first example of Pc-based thiol conjugated with quantum dots, revealed superior limiting characteristics with a limiting threshold below 0.18 J cm−2

Novelty Detection in the Design of Synthesis of Energy Storage Materials: a Case Study of Garnet-Structured Solid Electrolytes

Recent decades have shown arising growth-on-demand of integrating the machine learning into all areas of chemistry and materials science. In this study, we consider one of the aspects of applying these technologies to gain advantage in the search for new knowledge extracted from experimental data obtained in ever-growing number of studies. The novelty detection approaches are aimed to identify the artefacts in these data that may be of importance in many direc- tions. The analysis of "outliers" in details of the synthesis in the research studies of garnet-structured solid electrolytes was chosen as the object of demonstration of one of the practical applications of this methodology. Particular attention was paid to the choice of precursors. The thermodynamic data such as the heat of formation from the pure oxides as well as the results of drop solution calorimetry for simple oxides were involved as the descriptors of the studied systems. The overall performance of novelty/outlier detection of all types of outliers was characterized for the data described varying the complexity of description using ROC-AUC statistics and was assessed to be 0.71 – 0.72 using the Area-Under-Curve statistics. It was found that all “outlier” compounds related to those as the result of using the rare precursors in synthesis were successfully identified. The complementary regression analysis was performed to elucidate the relationship between the data diversity and the complexity of data description

Pauling Number as Efficient Descriptors for Screening the Structures with Negative Thermal Expansion Characteristics

In this study, the analysis of the known structure types demonstrating NTE was performed. Describing these structure types by the recently introduced and manifested parameter, Pauling Number (PN), showed that it is possible to circumscribe the candidate compounds with these characteristics by using this structure parameter since the flexibility of the compounds framework and the lattice topology are highly associated with the possibility of materials do not expand the lattice parameters while heating and to limit the changes of the structure during the possible phase transitions by, e.g., polyhedral tilting. We suggest that compounds with PN value close to those of the NTE materials can be considered as the targets for further investigation

Modeling ionic conductivity and activation energy in garnet-structured solid electrolytes: the role of composition, grain boundaries and processing

All-solid-state batteries (ASSBs) are one of the most forthcoming elements of the electrochemical energy systems of new generation. One of the most attractive perspectives of using all-solid- state batteries as the platform for energy storage is the increased safety, energy density and possible device miniaturization. During the last decades the intensive research of the solid state electrolyte materials has been observed. Among the most investigated and attractive candidates for Li-ion batteries one can distinguish the garnet-structured solid electrolytes, NASICONs, LGPS electrolytes and argyrodites. Despite the ever-growing interest to ASSB technologies there is a room in their chemistry to be explored especially concerning the aspects of the defects, vibrational characteristics, strain- and facet-engineering effects. The aim of this study is to investigate the possible role of composition, disorder and the synthesis details on the Li-ion conductivity and activation energies in garnet-structured solid electrolytes

A Machine Learning-Based Study of Li⁺ and Na⁺ Metal Complexation with Phosphoryl-Containing Ligands for the Selective Extraction of Li⁺ from Brine

The growth of technologies concerned with the high demand in lithium (Li) sources dictates the need for technological solutions garnering Li supplies to preserve the sustainability of the processes. The aim of this study was to use a machine learning-based search for phosphoryl-containing podandic ligands, potentially selective for lithium extraction from brine. Based on the experimental data available on the stability constant values of phosphoryl-containing organic ligands with Li+ and Na+ cations at 4:1 THF:CHCl3, candidate di-podandic ligands were proposed, for which the stability constant values (logK) with Li+ and Na+ as well as the corresponding selectivity values were evaluated using machine learning methods (ML). The modelling showed a reasonable predictive performance with the following statistical parameters: the determination coefficient R2= 0.75, 0.87 and 0.83 and root-mean-square error RMSE = 0.485, 0.449 and 0.32 were obtained for the prediction of the stability constant values with Li+ and Na+ cations and Li+/Na+ selectivity values, respectively. This ML-based analysis was complemented by the preliminary estimation of the host–guest complementarity of metal–ligand 1:1 complexes using the HostDesigner software