Benzene Fragments Research Articles

Effect of H<sub>3</sub>PO<sub>4</sub> and Phenol Additives on Gel Formation in Silica Fire Retardant Coatings for Building Materials

Increasing the fire resistance of wooden building structures is quite effectively ensured thanks to the development of fire-fighting compositions with aromatic components that contribute to the formation of a carbonized layer on the surface of the material during combustion. It is also known about the mutual positive influence of benzene fragments and phosphate-containing compounds on the fire-resistant characteristics of wood. The paper considers the possibility of complex use of phenol and orthophosphate acid to improve the flame retardant properties of SiO2-based coatings. The effect of modifying additives on the rheological properties of silicic acid sols was determined. Based on the results of IR spectroscopy, the influence of components on the nature of polycondensation in experimental SiO2 sols was evaluated. It is shown that the use of orthophosphate acid as a modifier leads to the initiation of predominantly linear polycondensation in experimental sols. It was established that small additions of phenol practically do not affect the course of polycondensation in experimental sols. Increasing the phenol content to 0.5% showed an effect on gel formation due to the possible addition of phenol to the skeletal silanol groups by the donor-acceptor mechanism, which makes it possible to have a synergistic effect of the complex additive of orthophosphate acid and phenol on the properties of the silica-containing flame retardant composition.

Synthesis, crystal structure and Hirshfeld surface analysis of 4'-cyano-[1,1'-biphen-yl]-4-yl 3-(benz-yloxy)benzoate.

In the title compound, C27H19O3N, the dihedral angle between the aromatic rings of the biphenyl unit is 38.14 (2)° and the C-O-C-C torsion angle in the benz-yloxy benzene fragment is 179.1 (2)°. In the crystal, the mol-ecules are linked by weak C-H⋯O inter-actions forming S(9) chains propagating along [010]. The most important contributions to the Hirshfeld surface arise from H⋯H (32.4%) and C⋯H/H⋯C (37.0%) contacts.

Classical and reactive simulations of plastic co-pyrolysis: Effects of polystyrene and its fragments on product yields, aggregation, and reaction mechanisms

Mixtures of polyethylene (PE), polypropylene (PP), polystyrene (PS), and their fragments such as ethylbenzene (EB) and linear alpha olefin (LAO) are simulated at different ratios using classical and reactive force fields. Using all-atom models validated by calculating conformations and diffusivities of differently sized PE melts in agreement with experiments, simulations are performed at 450 or 513 K that mimics a low temperature under the thermal co-pyrolysis condition, showing that the decomposition of PE into LAO influences densities and diffusivities of PE, to an extent dependent on PE lengths. In PE/PP/PS simulations, PS polymers aggregate at PS concentrations of 20 wt% or higher, leading to the separation between PS and other polymers. With the inclusion of EB that are assumed to be decomposed from PS, polymers do not aggregate. To understand reaction mechanisms, reactive simulations of PE and PS are performed, showing more heavy oil and less gas products at higher PS concentrations, in agreement with experiments, because PS fragments such as benzene, EB, and methylbenzene bind to PE and end up in heavy or light oils. In particular, the transfer of H radicals between PE and PS not only prevents further decomposition of polymers but also yields free radicals of polymers that can expedite co-pyrolysis. These findings help explain experimental observations regarding the effect of PS on liquid and gas product yields and suggest the optimal PS concentration without aggregation under the thermal co-pyrolysis condition, interpreted by reaction mechanisms of the transfer of H radicals and benzene fragments.

H8-BINOL-Derived Chiral η6-Benzene Ligands: New Opportunities for the Ruthenium-Catalyzed Asymmetric C-H Activation.

Given the tremendous success of (p-cymene)RuII-catalyzed C-H activation over the past 20 years, the community has long been aware that the development of chiral η6-benzene (Ben) ligands should be a potent strategy for achieving the attractive but incredibly underdeveloped ruthenium(II)-catalyzed asymmetric C-H activation. However, it has rarely been achieved due to the severe difficulty in developing proper chiral Ben ligands. In particular, designing chiral Ben ligands by connecting a benzene fragment to a chiral framework including benzene rings remained an unsolved challenge until this effort. Here we present a novel class of axially chiral Ben ligands derived from readily available (S)-5,5',6,6',7,7',8,8'-octahydro-1,1'-bi-2-naphthol ((S)-H8-BINOL) in 4-8 steps. Notably, when coordinated with ruthenium, such chiral Ben ligand containing three benzene rings only forms one of the three possible isomeric BenRuII complexes. The related chiral BenRuII catalysts could effectively catalyze the asymmetric C-H activation of N-sulfonyl ketimines with alkynes, affording a range of chiral spirocyclic sultams in up to 99 % yield with up to >99 % ee. These catalysts are expected to find broad applications in future.

H8‐BINOL‐Derived Chiral η6‐Benzene Ligands: New Opportunities for the Ruthenium‐Catalyzed Asymmetric C−H Activation

AbstractGiven the tremendous success of (p‐cymene)RuII‐catalyzed C−H activation over the past 20 years, the community has long been aware that the development of chiral η6‐benzene (Ben) ligands should be a potent strategy for achieving the attractive but incredibly underdeveloped ruthenium(II)‐catalyzed asymmetric C−H activation. However, it has rarely been achieved due to the severe difficulty in developing proper chiral Ben ligands. In particular, designing chiral Ben ligands by connecting a benzene fragment to a chiral framework including benzene rings remained an unsolved challenge until this effort. Here we present a novel class of axially chiral Ben ligands derived from readily available (S)‐5,5′,6,6′,7,7′,8,8′‐octahydro‐1,1′‐bi‐2‐naphthol ((S)‐H8‐BINOL) in 4–8 steps. Notably, when coordinated with ruthenium, such chiral Ben ligand containing three benzene rings only forms one of the three possible isomeric BenRuII complexes. The related chiral BenRuII catalysts could effectively catalyze the asymmetric C−H activation of N‐sulfonyl ketimines with alkynes, affording a range of chiral spirocyclic sultams in up to 99 % yield with up to >99 % ee. These catalysts are expected to find broad applications in future.

Solvatochromic fluorescent ethynyl naphthalimide derivatives for detection of water in organic solvents

Three new derivatives of (4-methoxyphenyl) ethynyl-naphthalimide were synthesized by Sonogashira coupling reaction. These compounds showed robust and strong fluorescent signals, which shift from blue to orange as the solvent polarity increases. Computational calculations revealed that in low-polarity solvents, the molecules preferred a 90° rotation between the naphthalimide and ethynyl benzene fragments. In high-polarity solvents, where the energy barrier for rotation of the alkyne bond was higher, the molecules favored the 0° conformer, leading to longer emission wavelengths. The compound with a 2-methoxyethyl group tethered to the naphthalimide nitrogen demonstrated sensitivity to water presence in the ranges of 0–30 % (v/v) in THF, 0–15 % (v/v) in DMSO, 0–30 % (v/v) in MeCN, 0–15 % (v/v) in acetone, and 0–40 % (v/v) in EtOH. The detection limits for water were determined to be 0.0523 %, 0.1365 %, 0.0337 %, 0.0570 %, and 0.1170 % (v/v) in THF, DMSO, MeCN, acetone, and EtOH, respectively. The effectiveness of this compound in quantifying ethanol content in spirit samples was successfully demonstrated.

1H NMR SPECTRAL CHARACTERISTICS OF PYRIDO[1,2-A]BENZIMIDAZOLE AND ITS DERIVATIVES

A systematic study of proton NMR spectra of pyrido[1,2-a]benzimidazole and 65 of its mono-, di- and poly-substituted derivatives with substituents in the pyridine and/or benzene fragment was carried out. The choice of certain structures is related to the great practical significance, as well as the complexity of interpreting their 1H NMR spectra. As a result of the research, a number of general patterns of arrangement (characteristic ranges) on the scale of chemical shifts of signals of hydrogen atoms associated with the nucleus of the studied heterocycles have been established. In the 1H NMR spectrum of pyrido[1,2-a]benzimidazole and most of its derivatives, the H1 signal of the pyridine cycle associated with a carbon atom was released in the weakest field, which experienced a strong electron acceptor effect of the nodal endocyclic nitrogen atom. The signal of another heteroaromatic proton H2 was usually detected in the strongest field region of the spectrum. The H8 signal had the smallest chemical shift among the aromatic protons. As the analysis of 1D 1H NOE spectra of a series of pyrido[1,2-a]benzimidazoles showed, this position of the heterocycle was the reaction center for the introduction of an electrophilic particle under SEAr reaction conditions. The H9 signal was detected in a weaker field relative to other aromatic protons. The influence of the electronic nature of the substituent and its position in the condensed heterocycle on the distribution of the electron density in the molecule has been established. It is concluded that the transmission of electronic effects of substituents in pyrido[1,2-a]benzimidazoles differs from benzoid systems. A number of controversial proton signals were attributed by means of 1H-1H NOESY and 1H-15N HMBC spectroscopy. The conducted studies will allow to use the data of 1H NMR spectroscopy to determine potential reaction centers in pyrido[1,2-a]benzimidazoles and other similar condensed pyridine derivatives with a nodal nitrogen atom. For citation: Begunov R.S., Fakhrutdinov A.N., Sokolov A.A., Savina L.I., Bashkov N.E. 1H NMR spectral characteristics of pyrido[1,2-a]benzimidazole and its derivativese. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 5. P. 43-53. DOI: 10.6060/ivkkt.20246705.6971.

Synthesis and crystal structure of a cadmium(II) coordination polymer based on 4,4′-(1H-1,2,4-triazole-3,5-diyl)dibenzoate

The asymmetric unit of the title compound, catena-poly[[[aquabis(pyridine-κN)cadmium(II)]-μ2-4,4′-(1H-1,2,4-triazole-3,5-diyl)dibenzoato-κ4 O,O′:O′′,O′′′] 4.5-hydrate], {[Cd(C16H9N3O4)(C5H5N)2(H2O)]·4.5H2O} n or {[Cd(bct)(py)2(H2O)]·4.5H2O} n (I), consists of a Cd2+ cation coordinated to one bct2– carboxylate dianion, two molecules of pyridine and a water molecule as well as four and a half water molecules of crystallization. The metal ion in I possesses a pentagonal–bipyramidal environment with the four O atoms of the two bidentately coordinated carboxylate groups and the N atom of a pyridine molecule forming the O4N equatorial plane, while the N atom of another pyridine ligand and the O atom of the water molecule occupy the axial positions. The bct2– bridging ligand connects two metal ions via its carboxylic groups, resulting in the formation of a parallel linear polymeric chain running along the [1\overline{1}1] direction. The coordinated water molecule of one chain forms a strong O—H...O hydrogen bond with the carboxylate O atom of a neighboring chain, leading to the formation of double chains with a closest distance of 5.425 (7) Å between the cadmium ions belonging to different chains. Aromatic π–π stacking interactions between the benzene fragments of the anions as well as between the coordinated pyridine molecules belonging to different chains results in the formation of sheets oriented parallel to the (\overline{1}01) plane. As a result of hydrogen-bonding interactions involving the water molecules of crystallization, the sheets are joined together in a three-dimensional network.

Thia[n]helicenes with long persistent phosphorescence.

Helicenes with persistent luminescence have received relatively little attention, despite their demonstrated highly efficient intersystem crossing (ISC) from the excited singlet to the triplet state. Herein, we designed a series of ortho-fused aromatics by combining dithieno[2,3-b:3',2'-d]thiophene (DTT) with annulated benzene fragments, denoted as TB[n]H (n = 3-8), to achieve persistent luminescence. Wherein, thia[n]helicenes (n = 5-8) exhibited intense phosphorescence with millisecond-range lifetimes (τp) at 77 K. Particularly interesting was the observation that the odd-numbered ring helicenes displayed longer τp values than their neighboring even-numbered counterparts. Notably, TB[7]H showcased the longest τp of 628 ms. This phenomenon can be attributed to the more favorable ISC channels and stronger spin-orbital coupling (SOC) of old-numbered helicenes than even-numbered ones. Furthermore, both conformers of TB[7]H exhibited significant circularly polarized phosphorescent (CPP) responses, with luminescence dissymmetry factors (glum) of 0.015 and -0.014. These discoveries suggest that thiahelicenes may be a specific class of organic phosphorescent and CPP materials.

DFT study on the adsorption of 1H-benzotriazole on the (1 1 1) surface of modelled Cu–25%Zn brass

The adsorption of 1H-benzotriazole (BTAH) on the (1 1 1) surface of modelled Cu–25%Zn brass is investigated using density functional theory calculations. In the one-atom modes, BTAH can uprightly adsorb on both copper and zinc sites via the N2 or N3 atoms of azole fragment and exhibit the σ-character interaction with the surface. The adsorption of BTAH in the two-atom modes is energetically more favorable than in the one-atom modes. However, the involvement of the zinc atom slightly decreases the adsorption strength of BTAH on the surface for both one-atom and two-atom modes. In the adsorption via the N2 atom, the dissociation barrier of BTAH on the copper atom is higher than on the zinc atom. By contrast, the exothermicity of dissociation reaction on the zinc atom is lower. The flat adsorption of BTAH exhibits a physisorption geometry on the surface of Cu–25%Zn without the strong interaction between the benzene fragment and the surface. With the dissociation, the N2 and N1 atoms move toward the zinc and copper atoms, respectively, and bond to them in the final state, resulting in the inclination geometry of the H-abstracted BTA with an angle of 25o between the molecular plane and the surface.

Polyphenylenepyridines Based on Acetylaromatic Compounds

Nitrogen-containing polyphenylene type polymers containing pyridine rings were synthesized. The polymer-forming reaction is based on the interaction of diacetylarylene and triethylorthoformate with the formation of a pyrylium salt and subsequent treatment of the intermediate product with ammonia. The optimal ratios of the reagents for the formation of the pyridine fragment were determined. The mechanism of the main reaction is discussed. The formation of the pyridine ring and phentriyl (1,3,5-triphenylsubstituted benzene) fragments was confirmed using 1H NMR data of the example of model reactions. After heating at a temperature of 450 °C, when a more complete polycondensation process occurs, the polymers reach high values of thermal characteristics—10% weight loss in an inert atmosphere corresponds to 600 °C. The structure of the synthesized polymers was confirmed using elemental analysis, IR, XPS, and EPR spectroscopy. The conjugation length in cross-linked polyphenylene pyridines can be controlled by varying the arylene bridge groups between the phentriyl fragments, which opens up opportunities for the development of new composite materials for electrical applications.

Crystal structure and Hirshfeld surface analysis of 1-[(E)-2-(3-nitro-phen-yl)diazen-1-yl]naphthalen-2-ol.

The title compound, C16H11N3O3, belongs to the family of azo dyes. In the light of a single-crystal X-ray study, it is evident that of the tautomeric forms (azo-hydrazone), the hydrazone form is the predominant form in the solid state, namely, (1E)-1-[2-(3-nitro-phen-yl)hydrazin-1-yl-idene]-1,2-di-hydro-naphthalen-2-one. The naphthol and benzene fragments attached to the -N=N- moiety adopt the s-trans conformation. Furthermore, the mol-ecules are nearly coplanar, subtending a dihedral angle of 2.63 (5)°. An intra-molecular N-H⋯O hydrogen bond occurs. There are only two types of inter-molecular inter-actions in the crystal structure: strong hydrogen-bonding C-H⋯O inter-actions and π-π stacking inter-actions. The importance of C-H⋯O inter-actions in the mol-ecular packing is reflected by the relatively high contributions (28.5%) made by O⋯H/H⋯O contacts to the Hirshfeld surface.

Sunlight Bleaching of Subporphyrazine Dye Films

Stable subphthalocyanine-type dyes with a high electron affinity attract much attention as potential substitutes for traditional fullerenes in molecular electronics devices. One possible way to enhance the acceptor properties of the subphthalocyanine core is by replacing the peripheral benzene fragments (C6H4) with 1,2,5-thiadiazole fragments (C2N2S1). However, the resistance of these materials to light or atmospheric effect remains an open question, which limits their further application in device manufacturing. In this work, we compare vacuum-deposited films of three derivatives, SubPzS3H0 (all peripheral fragments are 1,2,5-thiadiazoles), SubPzS2H4 (two fragments are 1,2,5-thiadiazoles and one fragment is benzene), and SubPcS0H12 (all benzenes, i.e., parent subphthalocyanine). Practically relevant substrates were used for deposition, namely, bare glass, glass/ITO or FTO, and PET/ITO. Photobleaching of films under continuous 1 sun illumination was studied in laboratory air, synthetic air, and ultrapure argon. It is shown that the exclusion of near-UV photons from the incident light spectrum, which corresponds to the absorption of subphthalocyanines in the Soret-band, strongly inhibits degradation. Absorption in the Q-band range initiates soft annealing rather than photobleaching of films. The stability of the films deposited on glass decreases as SubPzS3H0 > SubPzS2H4 > SubPcS0H12 in air, and vice versa in argon. The substrate adds more complexity to this picture. In argon, the ITO coating reduces degradation of all of the compounds equally, in contrast to the glass samples, while in air, the SubPzS3H0 films discolor completely. The latter reaction proceeds due to the indium-containing species migrating from the conductive coating.

IR, UV-visible, NMR spectra and aromaticity of the covalent organic tetraoxa[8]circulene frameworks

In this paper, we explore the aromaticity, electronic, vibrational and NMR spectra of the novel tetraoxa[8]circulene-based covalent organic frameworks which were first synthesized in 2022 [Angew. Chem. Int. Ed. 61 (2022) e202116527] being predicted by quantum chemical modeling in 2014 [Phys. Chem. Chem. Phys. 16 (2014) 6555–6559]. Both studied 2x2 and 3x3 tetraoxa[8]circulene (TOC) oligomers represent polyaromatic systems consisting of 108π (2x2) and 168π (3x3) electrons in the outer perimeter with a global diatropic (“aromatic”) current; they includes also two types of internal rings: the cyclooctatetraene cores with 8π electrons and larger C16(CH4)O4 cavities with 28π electrons. Both internal rings provide local paratropic (“antiaromatic”) ring currents.The elongated π-conjugated system of the 2x2 and 3x3 TOC oligomers is responsible for the unique nature of photoinduced charge transfer and vibrational spectra, which obey strict selection rules within the D4h symmetry point group. The nature of photoinduced charge transfer was interpreted using visualization methods including charge density difference and transition density matrix. It was found that strong optical absorption around 500 nm is for the doubly degenerated S3(4) (1Eu) states, in which one pair of oppositely located anthracene fragments has an alternating distribution of holes and electrons, while in the other pair of anthracene fragments, the holes and electrons are mainly localized on the central benzene fragments and the ethylene bridges of adjacent furan rings, respectively. For both 2x2 and 3x3 TOC oligomers, the optical absorption strength for S1 and S2 states is vanished. The density functional calculations of 2x2 and 3x3 TOC models have also allowed us to make the assignment of all the observed lines in the IR and Raman spectra of experimental pTOC samples. We believe that the TOC oligomers represent a new-generation of macrocyclic host molecules in heterocirculene and supramolecular chemistry.

Fluorenonophane chloro-benzene solvate: mol-ecular and crystal structures.

The title compound, 19 H,79 H-3,5,9,11-tetra-oxa-1,7(2,7)-difluorena-4,10(1,3)-dibenzena-cyclo-dodeca-phane-19,79-dione (fluorenonophane), exists as a solvate with chloro-benzene, C42H28O6·C6H5Cl. The fluorenonophane contains two fluorenone fragments linked by two m-substituted benzene fragments. Some decrease in its macrocyclic cavity leads to a stacking inter-action between the tricyclic fluorenone fragments. In the crystal, the fluorenonophane and chloro-benzene mol-ecules are linked by weak C-H⋯π(ring) inter-actions and C-H⋯Cl hydrogen bonds. The Cl atom of chloro-benzene does not form a halogen bond. A Hirshfeld surface analysis and two-dimensional fingerprint plots were used to analyse the inter-molecular contacts found in the crystal structure.

Development and Validation of a UV-Spectrophotometric Method for Quantitative Determination of Benzene Fragments in Benzyl Esters of Heparin

Development and Validation of a UV-Spectrophotometric Method for Quantitative Determination of Benzene Fragments in Benzyl Esters of Heparin

Quantum-chemical calculations of electronic spectra absorption: ab initio or semiempirical methods?

In order to develop approaches to predict the spectral properties of organic dyes for solar cells the test calculations of typical π-conjugated systems with various structural fragments, have been performed. Among the structural elements there are benzene, oxazole, oxsadiazole, thiophene and coumarin fragments. Nitro, methoxy, dimethylamino and diethylamino groups are substituents. According to the obtained experimental data, the diethylamino group at position 7 of the coumarin moiety gave the highest bato- and hyperchromic shifts of spectra. Experimental absorption spectra were measured in various solvents with different polarity. Among them are cyclohexane, dimethoxyethane, tetrahydrofuran, methanol, acetonitrile, and dimethylsulfoxide. It has been shown that there are no significant changes in the λ(max) absorption of coumarin-based compounds when the solvent is changed to a more polar one, but there is a noticeable tendency to increase the intensity of the absorption spectra. For the theoretical interpretations of electronic spectra absorption ab initio density functional theory (DFT) as well as semi-empirical methods (PPP/CIS, ZINDO/S, AM1/CIS) were used. In the DFT calculations the functionals B3LYP, CAM-B3LYP, M06-2x, PBE1PBE, wB97XD were used. A significant discrepancy in the estimations of electronic excitations is demonstrated by the DFT for the different functionals. It is concluded that DFT calculations should be performed by using both B3LYP and CAM-B3LYP (or M06-2x) functionals. Linear response theory has been used to evaluate the solvatochromic properties of π-conjugated compounds in the DFT frameworks. In general it was found that semi-empirical approaches especially π-electron method PPP/CIS and all valence method ZINDO/S can provide adequate estimations of excitation energies of π-conjugated dyes for moderate computer resources.

Position of the Benzene Ring Substituent Regulates the Excited-State Deactivation Process of the Benzyluracil Systems.

A systematic theoretical study of the regulating effect of the substituent position on the photoinduced deactivation process of the benzyluracil systems has been performed based on the high-level static electronic structure calculations and on-the-fly full-dimensional excited-state dynamics simulations. Similarities and differences coexist for the two systems by comparative studies on the photoinduced deactivation process of the 5-benzyluracil (5-BU) and 6-benzyluracil (6-BU) systems. They both obey an S2 → S1 → S0 two-step decay pattern, and the decay coordinates of the S2 → S1 and S1 → S0 processes are mainly driven by the elongation of the bridging bond and the out-of-plane ring deformation motion, respectively. However, the puckering motion occurring at the C2 atom in the uracil fragment dominates the decay pathway of the 5-BU system. On the contrary, the puckering motion at the C5 atom in the benzene fragment mainly drives the decay coordinate of the 6-BU system. Therefore, the substituent position could play significant roles in the deactivation process of the benzyluracil systems. Moreover, the S1 → S0 decay process of the 6-BU system consists of five pathways, possessing a more complex deactivation picture than the 5-BU system. The fitted time scale of the puckering motion is compatible with the experimentally observed lifetimes. This work provides a fundamental understanding of the photophysical and photochemical properties of the benzyluracil systems and can give rational suggestions to further design or regulate the bionic molecular systems.

Influence of heteroatom substitution in benzene rings on structural features and spectral properties of subphthalocyanine dyes

Peculiarities of the molecular geometry, electronic structure and spectral properties of heterocyclic subphthalocyanines analogues containing electron-deficient heterocycles have been considered using DFT and TD DFT methods. Subporphyrazine with annulated 1,2,5-selenadiazole rings was prepared and characterised for the first time and molecular parameters of the 1,2,5-thiadiazole analogue have been determined by single crystal X-ray diffraction. The theoretical results are compared with the experimental data and the effect of heteroatom substitution in benzene rings of subphthalocyanines on spectral-luminescence properties was revealed. Fusion of pyrazine, 1,2,5-thiadiazole or 1,2,5-selenadiazole rings instead benzene fragments leads to considerable stabilization of the frontier π-molecular orbitals of subporphyrazine macrocycle. The HOMO-LUMO gap is increased when pyrazine or 1,2,5-thiadiazole rings are fused, but becomes narrower in the presence of 1,2,5-selenadiazole rings. The intense Q band observed in the visible region (530–575 nm) originates from the lowest ππ* transition (2a2→1e*) and its energy follows the changes in HOMO-LUMO gap. Two transitions (2a1→1e* and 1a1→1e*) contribute predominantly to closely lying excited states (B1, B2) responsible for the intense Soret band in the UV-region (305–310 nm) of subphthalocyanine and its pyrazine and 1,2,5-thiadiazole analogues. For the Se-analogue the energy of the 2a1→1e* transition is decreased and B1 band is shifted bathochromically to 342 nm. Fusion of π-electron-deficient 1,2,5-chalcogenadiazole rings leads to appearance of the less intense band at 390 (S) or 408 nm (Se) due to electronic transition from HOMO 2a2 to 2e* orbital localized predominantly on peripheral heterocyclic fragments (CT band). The heavy atom effect of chalcogens decreases the fluorescence quantum yield in heterocyclic subphthalocyanines analogues, but promotes the intersystem crossing and strongly enhances the singlet oxygen quantum yield for 1,2,5-selenadiazole fused subporphyrazine (ΦΔ = 0.98 in CH2Cl2).

Out-cage metal ion coordination by novel benzoazacrown bisamides with carboxyl, pyridyl and picolinate pendant arms

A new series of macrocyclic diamides with carboxyl, pyridyl and picolinate pendant arms have been synthesized and the stability constants of their complexes with Ni2+, Cu2+, Zn2+, Cd2+, Pb2+ in water were determined. Complexes with a stoichiometry of 1 : 1 (M: L) were found for all ligands with the exception of 15-membered crown ethers with one pendant carboxyl or pyridine group. The ligand containing two picolinate backbone groups exhibits the highest values of the stability constants for all studied cations (logβML = 12.5–15.7). X-ray study of free ligands showed that the introduction of benzene and amide fragments into the macrocyclic moiety provides a flatten open structure of the ligand. The crystallographic analysis of Cu2+ and Zn2+ complexes revealed the external coordination of the metal atom by amine N atoms of the macrocycle and heteroatoms of the pendant groups.