The precise structure of the isolated molecule 4,4-difluoro-8-phenyl-4-bora-3a,4a-diaza-s-indacene (Ph-BODIPY) was determined by simultaneous gas-phase electron diffraction/mass spectrometry (GED/MS) in combination with quantum chemical calculations. It was found that Ph-BODIPY in the gas phase possesses an almost planar dipyrromethene skeleton with certain twist of the phenyl group with respect to the frame of the molecule. Since this is the first example of GED study of molecular structure of free BODIPY derivative, a choice of an appropriate approach of GED structural analysis in such cases was methodologically considered. The experimental equilibrium structure of Ph-BODIPY obtained in the work and the results of DLPNO-CCSD(T0) calculations were employed to evaluate the accuracy of various quantum chemical computations. The highest concordance with experimental data was achieved using calculations with the CAM-B3LYP functional, which, along with PBE0 and mPW1PW91, is recommended for a dependable description of the molecular geometry in similar systems.

The composition of the saturated vapors of two platinum complexes with the macrocyclic ligands 5,10,15,20-tetraphenylporphyrin (PtTPP) and 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (PtTF5PP) and their structures were determined by synchronous gas-phase electron diffraction/mass spectrometry (GED/MS). These porphyrin complexes are those with the heaviest metal atom in the coordination cavity that have been structurally investigated in the gas phase. The mass spectra confirm the presence of a single molecular form of each, PtTPP (T=629 K) and PtTF5PP (T=597 K). Their structures can serve as references for related complexes in the crystalline state or solutions. Differences between the geometries of PtTPP and PtTF5PP in the crystalline and gaseous states include a significant deformation of the tetrapyrrole macrocycle in solid PtTPP. The experimental Pt-N bond lengths of both complexes are in agreement with quantum chemical calculations (DFT/B97D/ECP(Pt)) taking into account relativistic effects. The effect of lanthanide contraction is evident from the similarity of the Pd-N and Pt-N internuclear distances of analogous compounds. The strong electron density transfer from the porphyrin backbone to the metal ion and the resulting low effective positive charge on the platinum atom, studied by NBO and QTAIM methods, helps to rationalize the high catalytic activity of such platinum compounds.

The equilibrium structure of free 4-(4-hydroxyphenylazo)phthalonitrile (p-HPhAPN, C14N4H8O) molecules was investigated for the first time by combined gas-phase electron diffraction and mass spectrometry (GED/MS) experiment, as well as through quantum chemical (QC) calculations. It was determined that p-HPhAPN in the vapor is represented by planar azo forms. & Scy;is-trans isomerism, azo-hydrazone tautomerism and rotations of different moieties in p-HPhAPN were studied in B3LYP-D3/pcseg-2 and DLPNO-CCSD(T0) levels of theory. Electron impact mass spectra of p-HPhAPN are typical for azobenzenes and are interpreted using the results of QCxMS calculations at the GFN2-xTB level of theory. Due to the exciting possibility of p-HPhAPN in the preparation of phthalocyanines with macrocyclic and azo chromophores, the structures of corresponding isomers of zinc phthalocyanines were investigated.

A comprehensive study of the structural, spectral and energetic properties of chloroboron(III) complexes of subphthalocyanine (H(12)SubPc, for the first time) and dodecafluorosubphthalocyanine (F(12)SubPc, reinvestigation) was performed by mass-spectroscopy (MS), gas-phase electron diffraction (GED), IR spectroscopy and quantum-chemical (QC) calculations. A synchronous GED/MS method showed that at T = 630 K and T = 540 K, thermally stable H(12)SubPc and F(12)SubPc molecular forms are present in the gas phase. The geometric structure of free molecules has been determined, in which the N-3-B-Cl fragment has the structure of a distorted tetrahedron, and the phthalocyanine skeleton has a dome shape. QC calculations of the geometry agree well with the GED results. The similarities and differences of the molecular structure in the gas and solid phases were discussed. It is shown, that despite the similarity of most geometric parameters, the H(12)SubPc and F(12)SubPc have significant differences in electronic characteristics, which determines the differences in their physicochemical properties. The interpretation of the experimental IR spectra was carried out. The distribution of potential energy of normal vibrations over the internal vibrational coordinates has been analyzed. The sublimation enthalpies of H(12)SubPc (Delta H-s(589 K) = 135(5) kJ & sdot; mol(-1)) and F(12)SubPc (Delta H-s(516 K) = 189(3) kJ & sdot; mol(-1)) were determined by the mass spectrometric Knudsen effusion method. The obtained data is important for designing processes employed in fabricating optoelectronic devices based on subphthalocyanines by PVD. Experimental geometric parameters for free molecules and vibrational frequencies can be used to calculate the thermodynamic functions of gaseous H(12)SubPc and F(12)SubPc.

The geometrical re parameters of trans-azobenzene (E-AB) free molecule were refined by gas electron diffraction (GED) method using available experimental data obtained previously by S. Konaka and coworkers. Structural analysis was carried out by various techniques. First of all, these included the widely used molecular orbital constrained gas electron diffraction method and regularization method. The results of the refinements using different models were also compared—a semirigid model, three variants of one-dimensional dynamic models, and a two-dimensional pseudoconformer model. Several descriptions have been used due to the fact that E-AB has a shallow potential energy surface along the rotation coordinates of phenyl groups. Despite this, it turned out that the semirigid model is suitable for use for E-AB and allows good agreement with experimental data to be achieved. According to the results of GED structural analysis, coupled with the results of DLPNO-CCSD(T0) calculations, E-AB has a planar structure. Based only on GED data, it is impossible to unambiguously determine the rotational angle of the phenyl group due to the facts that (i) with rotation over a wide range of angles, the bonded distances in the molecule change insignificantly and (ii) potential function in a structural analysis within a dynamic model is not determined with the necessary accuracy. This work also examines the sensitivity of the GED method to structural changes caused by trans-cis isomerization. The paper also analyzes the applicability of different variants of density functional theory (DFT) calculations in GED structural analysis using E-AB as an example. There are not enough similar methodological works in the literature. This experimental and methodological information is especially important and relevant for planning and implementing GED experiments and corresponding processing of the results for azobenzene derivatives, in which the conformer and isomeric diversity are even more complicated due to the presence of different substituents.

The processes of supramolecular self-assembly of Co(III)-meso-tetra-(4-trimethylammoniophenyl)porphyrin (CoP) and bis-(4-(1-imidazolyl)-phenol)-Sn(IV)-meso-tetra(4-sulfophenyl)porphyrin (SnP) were studied using electronic, steady-state and time-resolved fluorescence, one- and two-dimensional NMR spectroscopy in aqueous media. The main product of such interaction at a 2:1 M ratio of Co and Sn porphyrinates was found to be supramolecular porphyrin trimer CoP-SnP-CoP formed due to donor-acceptor, hydrogen and electrostatic interactions. The distinctive features of the resulting trimer are: significant distortion of the spatial structure of the Co-porphyrin fragments and strong quenching of the Sn-porphyrin macrocycles fluorescence (by 70 %). The distortion of the spatial structure of Co porphyrinates is in good agreement with the quantum chemical calculations as well as with the electronic and NMR spectroscopy data. Adding surfactants - both anionic (Cetyltrimethylammonium bromide - CTAB) and cationic (Sodium dodecyl sulfate - SDS) - even at concentrations below the critical micelle concentration (CMC) leads to the supramolecular trimer destruction. In solutions of ionic surfactants, supramolecular trimer destruction is caused by the interaction of either the peripheral macrocycles of the trimer (CoP) with SDS micelles (premicellar aggregates) or the central macrocycle (SnP) with CTAB micelles (premicellar aggregates). This process is prolonged and the rate of trimer destruction depends on the surfactant concentration. The sizes of the CTAB and SDS micelles solubilized with porphyrin molecules were established by dynamic light scattering. In general, surfactant additions lead to an increase in the SnP fluorescence at least due to the destruction of the supramolecular self-assembly, as well as due to the changes in the state of its microenvironment.

Gas-phase electron diffraction and quantum chemical study of the isolated H2TPP molecule was carried out, which can be considered as a reference point for tetraphenylporphyrin metal complexes. Using Knudsen effusion mass spectrometry, the enthalpy of sublimation of the H2TPP was determined to be 212(4) kJ/mol (535 K). Using DFT/B97D/cc-pVTZ in combination with gas electron diffraction it is shown that the saturated vapor of H2TPP consists of a mixture of conformers. The conformers differ in the mutual orientation of the four phenyl fragments relative to each other and have close energies. Bond lengths and bond angles in conformers were determined. NBO analysis showed a change in the delocalization of the electron density between the phenyl substituents and the macroheterocyclic (MHC) skeleton with a change in the torsion angle. This delocalization is the reason for the non- orthogonal position of phenyl meso-substituents in the conformers of H2TPP and other tetraphenyl substituted porphyrins. Non-covalent interactions between the MHC skeleton and phenyl substituents have been described using the FI-SAPT0 method. The change in geometric and electronic characteristics in the series of molecules H2P, H2TPP, H2FTPP, ZnTPP and PdTPP is considered. Based on Valence Shell Electron Pair Repulsion (VSEPR) theory, an explanation is given for the influence of the substituent on the parameters of the MHC skeleton. Analysis of changes in the energy of frontier orbitals in the indicated series of molecules makes it possible to predict the direction of changes in the red-ox properties of compounds with various modifications ofH2TPP.

Structural features, conformational manifold and isomeric forms of 4-(4-hydroxyphenylazo)phthalonitrile (p-HPhAPN) were studied by DFT calculations (B3LYP) using QTAIM, NPA, NBO, NCI, SAPT0 analysis. The influence of hydroxyl and nitrile groups on the geometric structure of the molecule was analyzed in comparison with the initial azobenzene and isomers differing in the location of the hydroxyl group - m-HPhAPN, o-HPhAPN. For the initial p-HPhAPN, 8 possible models were considered, for isomeres o-HPhAPN and m-HPhAPN - 32 and 16 models, respectively. The variety of the chosen models is due to the possibility of (a) different arrangement of hydrogen atoms of the hydroxyl group, determined by the corresponding torsion angle, (b) cisoid/transoid arrangement of nitrile groups with respect to the azo group, (c) cisoid/transoid arrangement of the hydroxyl group with respect to the azo group, (d) tautomerism, and (e) cis-trans isomerism. Assignment of vibrational modes of p-HPhAPN was carried out via potential energy distribution (PED) analysis among internal coordinates. The PED of most normal vibrations for p-HPhAPN, as well as for initial azobenzene, has a complex character. Changes in the IR spectra caused by the considered structural changes are noted.

Structural, spectroscopic and thermodynamic studies carried out in the scientific labora-tories of the Physics Department of the Ivanovo State University of Chemistry and Technology in the last 5-10 years are briefly reviewed.

Semi-experimental gas-phase structures of anthracene and rubrene (5,6,11,12-tetraphenyltetracene) were determined by means of gas electron diffraction (GED). The use of the flexible restraints in the refinement of the GED data successfully resolves non-equivalent C-C bond lengths. The tetracene core of an isolated rubrene molecule was found to exhibit a twist distortion of about 18°; this is less than DFT calculations predict (30-40°). The modified Feller-Peterson-Dixon method in conjunction with high-level DLPNO-CCSD(T) calculations was employed to resolve the discrepancy between the available experimental gas-phase enthalpies of formation for rubrene. The theoretical value of meets its recent experimental counterpart (765.6 ± 8.4 kJ mol-1) and is in strong disagreement with the previous estimation (882 kJ mol-1).

Synthesis of two platinum complexes, 5,10,15,20-tetraphenylporphyrin (PtTPP) and 5, 10,15,20-petyluorotetraphenylporphyrin (PtTF 5 PP), is described. IR spectra of the complexes and metal-free 5,10,15, 20-tetraphenylporphyrin (H2TPP) were obtained in KBr tablets. Structural parameters of conformers were optimized using DF77/B3LYP/cc-pVTZ (C,N,H,F), aug-cc-pVTZ-PP, ECP (Pt), and their vibration frequencies were calculated. Conformers differ mainly in angles of rotation of substituents at meso-position relative to macrohetemcyclic backbone. For H2TPP, the most stable conformer possesses C-2 nu symmetry, for PITPP -D-2d, and for PtTF5PP- D 4th. Energy difference between conformers of each molecule does not exceed 1.1 kJ/mol. Experimental and theoretical IR spectra are presented, their comparison determines the scaling factor (0.977) for theoretical vibration frequencies of all three molecules in the range of 500-1700 cm(-1). Interpretation of experimental IR spectra has been performed. For all frequencies of normal vibrations, the potential enelgv distribution along the internal vibrational coordinates is analyzed. The spectra of the three compounds in the range of 2800-3400 cm(-1). differ from each other. The IR spectrum of the H2TPP compound contains a band at 3370 cm(-1), which belongs to the stretching vibration nu(N-H), while the IRS of the PtTF5PP compound lacks a band at 2925 cm(-1) belonging to the v(C pb -H) vibrations ofphenyl fragments. The frequencies v(N-H), nu(C-b-H) and nu(C-ph-H) correlate with the values of corresponding internuclear distances. The shorter the bond length, the higher the force constant of stretching of this bond and the higher the frequency of the stretching vibration. Introduction of platinum atom into coordination cavity changes the relative intensity of bands in region of 500-1700 cm(-1) and decreases their number, which is associated with an increase in the symmetry of PtTPP and PITF5PP molecules as compared to H2TPP. Most of vibrational modes in the region of 500-800 cm(-1) are mixed and represent a linear combination of several internal coordinates. They refer to nonplanar out-of-plane vibrations of macroheterocyclic backbone, as well as to nonplanar deformations of carbon skeleton in the -C6H5 and -C6F5 substituents. Frequencies in the range 900-1600 cm(-1) mainly refer to stretching vibrations of C-a-C-b, C-ph-C-ph, C-a-C-m, C-a-N, C-F bonds, as well as to plane and non-planar vibrations associated with a change in bond angles of C-a-C-b-H in the backbone and C-ph-C-ph-H angles in the -C6H5 substituents. The calculated IR spectra in the low-frequency region up to 500 cm(-1) reflect the structural nonrigidity of molecules and correspond to vibrations at which the macrocyclic backbone of the dome, raffling, and wave type is distorted, as well as distortions occurring in plane of the backbone. The same region contains the frequencies of torsional vibrations of-C6H5 and -C6F5 substituents. Difference in the IR spectra is considered and the characteristic frequencies of three compounds are determined A distinctive feature of IR spectrum of PtTF5PP is the presence of intense absorptions, which belong to C-F stretching vibrations of different symmetry, and which are absent in IR spectra of H2TPP and PtTPP. H2TPP spectrum contains a band at 883 cm(-1), which is associated with a combination of vibrational coordinates r(C-al-C-b1(2)) and r(C-a2-C-b2) in two nonequivalent fragments. This band is absent in the IR spectrum of platinwn complexes. The relationship between the geometric parameters and frequencies of stretching vibrations of H2TPP, PtTPP, and PtTF5PP molecules is shown.

Molecular parameters of 5,10,15,20-tetrakis(4'-fluorophenyl)porphyrin were determined for the first time by gas-phase electron diffraction. Conformational preference was investigated based on the experimental data and was found to be in the good agreement with the preliminary model-based considerations. The experimental vibrational spectrum was measured and assigned. The structural features were compared with that of the previously studied Zn(II) and Pd(II) complexes with tetraphenylporphyrin. The results of the Knudsen effusion mass spectrometry experiment yielded the value of the sublimation enthalpy of Delta H-sub degrees(584 K) = 233(4) kJ mol(-1). The introduction of substituents into the paraposition of phenyl fragments does not significantly affect the electron density distribution and geometry of the coordination cavity. (C) 2020 Elsevier B.V. All rights reserved.

Conformational manifold of 5,10,15,20-tetrakis(4¢-halogenophenyl)porphyrins (p-4C6H4X-H2P; X=F, Br) was studied by DFT calculations (functional B3LYP). The conformers are different by positions of -4C6H4X groups relative to the macrocyclic core. Relative energies of the conformers of 4C6H4F-H2P were calculated with use of different basis sets in order to find the optimal ratio «quality/ computational cost». According to the results of the calculations, conformers of C2V symmetry are the most energetically favorable. However, relative energies of other conformers are quite low, therefore they should be taken into account at the treatment of the gas-phase electron diffraction (GED) experimental data. The sensitivity of the GED method to structural changes induced by different relative positions of halogenophenyl substituents was examined. Model radial distribution curves f(r) for conformers of p-4C6H4X-H2P, as well as meta- and ortho- isomers (m-4C6H4X-H2P and o-4C6H4X-H2P) were compared. The results of the model studies demonstrate that the bond distances can be reliably determined from experimental data, while the refinement of the positions of halogenophenyl substituents relative to the macrocyclic core is at the limit of the possibilities of the GED method. Meta- and ortho- isomers of 4C6H4X-H2P can be distinguished based on the experimental data, especially in the case of bromine-substituted phenyl groups.