Low-symmetry A3B-type 6H-1,4-diazepinoporphyrazines with anti-Kasha effect as promising photosensitizers

A series of tribenzo[g,l,q]-6H-1,4-diazepino[2,3-b]porphyrazines has been synthesized. A temperature-dependent steric effect was applied in the mixed Linstead macrocyclization of phthalonitrile and 5,7-bis(2'-arylethenyl)-6-propyl-6H-1,4-diazepine-2,3-dicarbonitrile to achieve high yield of low-symmetry A3B-type Mg(II) tribenzo[g,l,q]-6H-1,4-diazepino[2,3-b]porphyrazinate. The analysis of photophysical and photochemical properties of the obtained complexes showed the anti-Kasha effect: the ultrafast spin changes successfully compete with the IC. TD-DFT calculations showed that the presence of 1,4-diazepine heterocycle in the porphyrazine structure leads to the formation of additional charge-transfer triplet state T2. We propose, it could participate in the pumping of T1x state alongside with T1y state (these states are degenerate in D4h symmetry) and, therefore, increase singlet oxygen (1Δg) generation. Stable micellar nanoparticles have been obtained based on the tribenzo[g,l,q]-6H-1,4-diazepino[2,3-b]porphyrazine Mg(II) and Zn(II) complexes using polyvinylpyrrolidone. The nanoparticles effectively interact with model biological structures (FBS and brain homogenate), leading to disaggregation of the macrocycles. They also exhibit pronounced phototoxic effects in MCF-7 cells upon red light irradiation. We propose that enhancement in PDT activity could be explained by their increased resistance to aggregation due to the presence of n-propyl substituent directly attached to the C6 position of the 1,4-diazepine moiety. The demonstrated results show the promising potential of tribenzo-6H-1,4-diazepinoporphyrazines as heavy atom-free photosensitizers.

Electronic and steric effects controlling monomer-dimer self-assembly in 6H-1,4-diazepinoporphyrazines: an experimental and theoretical study

A series of 5,7-disubstituted 1,4-diazepinoporphyrazinato magnesium(II) and nickel(II) complexes, including two novel compounds, were obtained by metal-templated macrocyclization. A combination of X-ray diffraction, ¹H NMR, UV-vis, and electrochemical analyses allowed us to study their tendency towards H-type dimerization and trace the influence of structural and solvation factors on dimer stability. Based on the physicochemical and theoretical DFT calculation data, it was found that the main binding forces between 6H-1,4-diazepinoporphyrazine decks in the dimers were efficient π-π donor-acceptor interactions induced by the interdeck C-H⋯N hydrogen bonds. Furthermore, the metal-ligand (Pz^2- → M²⁺) electronic interactions have a key influence on the π-π stacking of the porphyrazine cores. It was shown that the displacement of the metal ion out of the macrocycle plane induced by coordinating agents can trigger the dissociation of the dimer, since the resulting enhancement of the donor-acceptor electronic interaction between the metal ion and the π-system of the ligand leads to a subsequent weakening of the π-π stacking of the porphyrazine cores. The TD-DFT calculations predicted the non-degeneracy of the HOMO-1 → LUMO and HOMO → LUMO+1 transitions in the 6H-1,4-diazepinoporphyrazine H-dimers, which explains the Q-band splitting in their UV-vis spectra.

Porphyrazines with annulated diazepine rings. 6. Synthesis and properties of the alkyl substituted derivative - MgII complex of tetrakis-2,3-(5,7-di-tert-butyl-6H-1,4-diazepino)porphyrazine

Novel MgII porphyrazine 3 bearing four appended seven-membered tert-butyl substituted 1,4-diazepine rings was prepared via Linstead macrocyclization of 5,7-di-tert-butyl-6[Formula: see text]-1,4-diazepine-2,3-dicarbonitrile 2, obtained by condensation of diaminomaleonitrile and 2,2,6,6-tetramethylheptanedione-3,5 (1) in anhydrous ethanol in the presence of P2O5. The structure of the dinitrile precursor 2 was established by single crystal X-ray work. 1H NMR study revealed that the 1,4-diazepine ring is present in the 6[Formula: see text] tautomeric form both in the dinitrile precursor 2 and the MgII complex 3. The inversion of the tert-butyl substituted diazepine ring occurs more easily than in the case of aryl and alkenyl substituted species. Although porphyrazine 3exhibit some tendency to aggregation in low-polar solvents the presence of bulky tert-butyl substituents stabilizes the monomeric form and hinders formation of H-bonded dimers characteristic for aryl and styryl substituted analogues.

Synthesis and characterization of heteroleptic rare earth double-decker complexes involving tetradiazepinoporphyrazine and phthalocyanine macrocycles

Reaction of (2,3,9,10,16,17,23,24-octabutylphthalocyaninato)lanthanide(iii) acetylacetonates (BuPcLn(acac), 1a-c, Ln = Lu (a), Eu (b), La (c)) with a tetrakis(5,7-bis(4-tert-butylphenyl)-6H-1,4-diazepino)[2,3-b,g,l,q]porphyrazine ligand (tBuPhDzPzH2, 2) produced sandwich compounds (tBuPhDzPz)Ln(BuPc) (3a-c), which represent the first heteroleptic double-deckers incorporating both Pc and DzPz decks. A combination of high-resolution mass spectrometry, UV-Vis/NIR, MCD, and 1H NMR spectroscopy, and square-wave voltammetry provided unambiguous characterization of target complexes 3 indicating that their spectral and electrochemical properties are generally intermediate with respect to their homoleptic relatives. Based on the data of solution-state 1H-1H NMR (COSY, NOESY) correlation spectroscopy supported by DFT calculations, a dimerization tendency of compounds 3 proportional to the Ln(iii) ion size was found. The spectroelectrochemical study of 3 and the corresponding homoleptic double-deckers revealed a pronounced tendency to aggregation of the one-electron oxidized forms of DzPz-containing double-decker complexes compared to homoleptic Pc2Ln compounds.

Porphyrazines with annulated diazepine rings. 5. Near-IR-absorbing tetrakis(6,7-dihydro-1H-1,4-diazepino)porphyrazines and effects of acid solvation on their spectral properties

Novel porphyrazines bearing fused 6,7-dihydro-1H-1,4-diazepine rings were synthesized and their spectral response on the change of medium acidity was demonstrated.

Optical readout of controlled monomer-dimer self-assembly

5,7-Substituted 1,4-diazepinoporphyrazine magnesium(ii) complexes were synthesized via Mg(ii)-alkoxide templated macrocyclization. A single crystal growth synchrotron diffraction analysis permitted what is to our knowledge the first structural characterization of a 1,4-diazepinoporphyrazine. It exists as a dimer in the solid state. In silico calculations supported by solution phase spectral studies involving a series of representative derivatives, provided insights into the factors governing dimerization of 1,4-diazepinoporphyrazines. The present 1,4-diazepinoporphyrazines serve as useful probes for understanding the determinants that guide dimer-monomer equilibria and the self-assembly of phthalocyanine derivatives.

Photophysical properties and photocytotoxicity of free and liposome-entrapped diazepinoporphyrazines on LNCaP cells under normoxic and hypoxic conditions

5,7-Diaryl-substituted symmetrical diazepinoporphyrazine and tribenzodiazepinoporphyrazine were synthesized and characterized using UV-Vis, MS MALDI, and various NMR techniques. The expected photosensitizing potentials of these porphyrazines were evaluated by measuring their abilities to generate singlet oxygen in organic solvents and by comparing them with that of the recently obtained dendrimeric G1-type diazepinoporhyrazine. Absorbance and fluorescence measurements were performed to study the aggregation properties of the novel macrocycles. The photocytotoxicity of tribenzodiazepinoporphyrazine towards LNCaP cells in its free form and after its incorporation into liposomes was examined using MTT assay under normoxic and hypoxic conditions. It is interesting that all tested liposome formulations maintained their phototoxic activity in hypoxia. Also, tribenzodiazepinoporphyrazine incorporated into liposomes revealed better photocytotoxic effect (IC₅₀ values of 0.600 ± 0.357 μM and 0.378 ± 0.002 μM) than its free form (IC₅₀ values of 3.135 ± 0.156 μM). Following the in vitro experiments, the most promising liposomal formulation containing l-α-phosphatidyl-DL-glycerol for tribenzodiazepinoporphyrazine was found. Moreover, tribenzodiazepinoporphyrazine incorporated into liposomes containing 1,2-dioleoyl-3-trimethylammonium-propane (chloride salt) revealed moderate phototoxicity at 5 × 10^-5 μM for antibacterial photodynamic therapy. It was established that an irradiation of planktonic bacterial strains significantly reduced CFUs of Staphylococcus aureus ATCC 25923 in comparison to tribenzodiazepinoporphyrazine containing l-α-phosphatidyl-DL-glycerol liposomes.

5,7-Bis(2'-arylethenyl)-6H-1,4-diazepine-2,3-dicarbonitriles: synthesis, and experimental and theoretical evaluation of the effects of substituents at 5,6,7-positions on the molecular configuration and spectral properties

A series of novel 5,7-bis(2'-arylethenyl)-6H-1,4-diazepine-2,3-dicarbonitriles was synthesized through sequential aldol condensation reactions of 1,3-diketones with diaminomaleonitrile, and the resulting 5,7-dimethyl-6H-1,4-diazepines were condensed with aromatic aldehydes. The substituents' effects on the spectral properties and conformational states of the molecules in solution were studied using 2D NMR techniques and DFT calculations. Specific intramolecular steric interactions in derivatives substituted at the C6 position were discovered and investigated in detail. Differential scanning calorimetry and thermogravimetric analyses revealed the strong dependence of the thermal stability of the newly prepared diazepinodicarbonitriles on the nature of the substituents. This offers new insight into the structure-property relationships of arylethenyl-substituted diazepine derivatives.

Double-decker bis(tetradiazepinoporphyrazinato) rare earth complexes: crucial role of intramolecular hydrogen bonding

Study focuses on specific interactions in diazepine-containing macroheterocycles.

Novel A₃B-type tert-butyl-substituted tribenzodiazepinoporphyrazine: synthesis, spectral properties and DFT study

Novel A3B-type 8(9),13(14),18(19)-tri-tert-butyl-2(5),4(7)-bis(4-tert-butylphenyl)tribenzo[g,l,q]-6H-1,4-diazepino[2,3-b]porphyrazine, which has high solubility in organic solvents, was obtained by template co-condensation of 2,3-dicyano-5,7-bis(4-tert-butylphenyl)-6H-1,4-diazepine and 4-tert-butylphthalonitrile. It was characterized by UV/Vis, (1)H, (13)C NMR spectroscopy, and MALDI-TOF/TOF mass spectrometry. We have demonstrated for the first time using fluorescence spectroscopy measurements and quantum-chemical calculations that the complicated UV/Vis spectrum of A3B-type tribenzodiazepinoporphyrazine is due to the formation of stable H-type aggregates.

Cerium bis(tetradiazepinoporphyrazinate): synthesis and peculiarities of spectral and electrochemical behavior

A cerium sandwich double-decker complex of tetradiazepinoporphyrazine was synthesized for the first time, which exhibited specific spectral and electrochemical properties.

The first synthesis of sandwich-type complex based on tetradiazepinoporphyrazine ligand

Sandwich-type complex based on tetradiazepinoporphyrazine ligand — bis{tetrakis(5,7-di(4-tert-butylphenyl)-6H-1,4-diazepino)[2,3-b,g,l,q]porphyrazinato}lutetium — was synthesized for the first time. The structure of the compound has been confirmed by UV-vis/NIR, 1 H NMR spectroscopy, and MALDI-TOF mass spectrometry data. The introduction of annulated diazepine heterocycles to porphyrazine molecule significantly changes macrocycle reactivity and results in sandwich-type complex under conditions used for the selective synthesis of lanthanide(III) monophthalocyanines.

Porphyrazines with annulated diazepine rings 4: Synthesis and properties of MgII tetradiazepinoporphyrazine carrying exocyclic styryl fragments

A novel tetradiazepinoporphyrazine MgII complex bearing eight peripheral styryl substituents, [St8TDzPAMg(H2O)] ( St = -CH=CHAr , where Ar = 4-methoxyphenyl ) was prepared by template cyclotetramerization of the corresponding precursor — 5,7-distyryl substituted diazepino-2,3-dicarbonitrile — in the presence of MgII butoxide in n-butanol. UV-visible and 1H NMR spectral data indicate that the complex is strongly aggregated in non-coordinating solvents (dichloromethane, chloroform, benzene), it is dimeric in pyridine, whereas it is predominantly monomeric in dimethylsulfoxide and dimethylformamide. The fluorescence response is high for solutions in which the monomeric form is prevalent, but it is strongly quenched as the content of the dimer is increased. Evidence was obtained that dimerization occurs due to intermolecular hydrogen bonding between acidic CH2 groups in the diazepine ring (6H form) of one molecule with meso- and/or diazepine N atoms of another molecule, dimerization being also contributed by the presence of chlatrated water. In the presence of fluoride anions the dimer is destroyed with formation of the monomeric species, which is changed to the 1H form upon heating, as indicated by 1H NMR spectra.