Peripheral Substituents Research Articles

Charge-by-Charge Ion Pairing Preserves Fluorescence Emission

In this issue of Chem, Flood and co-workers demonstrate spatially and electronically isolated cationic dyes in crystalline charge-by-charge ion-pairing systems based on sandwiched [2 + 1]-type anion complexes of a π-electronic cyanostar macrocycle; these dyes exhibit fluorescent colors and intensities similar to those in solution.

An Alternative Approach to the Hydrated Imidazoline Ring Expansion (HIRE) of Diarene‐Fused [1.4]Oxazepines

A four‐step approach to the “hydrated imidazoline ring expansion” (HIRE) is presented. In most cases, the ring expansion was the sole process. However, for the first time, an alternative course of the hydrated imidazoline evolution was discovered which gave N‐aminoethyl derivatives. These can, in principle, be converted into the target HIRE products under sufficiently forcing conditions. The approach offers improved flexibility with respect to the peripheral substituents and is also applicable to the synthesis of eleven‐membered lactams. We observed that the latter can exist in two stable isomeric forms due to lactam–amide bond isomerization. The latter finding further demonstrates the value of medium‐sized rings as multiple‐conformer probes for biological target interrogation.

Structure–Activity Relationship of the Polymerized Cobalt Phthalocyanines for Electrocatalytic Carbon Dioxide Reduction

Polymeric frameworks composed of molecular complexes have been attractive for the outstanding activity, selectivity, and stability toward CO2-to-CO conversion. In this work, polymerized cobalt phthalocyanines (CoPPc) with different functionalities were investigated with a series of spectroscopy characterizations, controlled-potential electrolysis, Tafel analysis, cyclic voltammetry analysis, and isotope labeling studies. The electronic structure of the Co center was revealed to be directly affected by the peripheral substituents via an inductive effect. Besides, the relationship between electronic structure and activity of the CoPPc-based catalysts for CO2 electroreduction was successfully elucidated at the molecular level.

The potential occurrence modes of hydrocarbons in asphaltene matrix and its geochemical implications

As the most polar component of crude oils, asphaltenes are characterized by their complex molecular structures and their sequestration of small organic molecules. These organic compounds are often protected from various secondary alteration processes, and thus might serve as useful molecular markers. However, little is presently known about the mode of occurrence of hydrocarbons isolated from asphaltenes by conventional approaches. In the current study, we collected veined bitumen samples from the Changjianggou Formation of the Longmen Mountains on the northwestern rim of the Sichuan Basin, extracted soluble organic matter with dichloromethane, precipitated asphaltenes with petroleum ether, and isolated hydrocarbons from the asphaltenes by centrifugation and hydrous pyrolysis. The results indicated that the n-alkane profiles of saturated hydrocarbons obtained by centrifugation and by hydrous pyrolysis at 300 °C not only were similar to each other, but also resembled those of typical crude oils more closely than the n-alkane profiles of the saturates fraction in veined bitumen extracts did. The asphaltene-bound aromatic hydrocarbons and resins were found to be too difficult to extract thoroughly by the current separation methods. A possible explanation is that saturated hydrocarbons are mostly associated with the peripheral substituents of asphaltenes via hydrophobic association, whereas aromatics and resins tend to interact with the asphaltene cores through π-π stacking, which is much stronger. Therefore, the dissociation or diffusion of the loosely bound saturated hydrocarbons would alter the geochemical information that they had originally recorded, whereas the covalently bonded or more tightly associated hydrocarbons are better shielded from secondary alteration processes.

Electrochemical Properties of Mono- and Bis-CN Ligated Cobalt Corroles

Corroles have attracted a great deal of attention in terms of application and understanding their electronic configuration, especially the innocence or non-innocence of the macrocyclic ligand. These properties are known to be strongly influenced by the metal ion and degree of axial coordination, namely 4, 5 and 6-coordinate. In addition, these properties are also dependent on the solvent and possibly peripheral substituents. We have previously examined bis-pyridine and mono-DMSO cobalt corroles and in this work describe the electrochemical and spectroscopic properties of newly synthesized series of anionic axially ligated mono-CN and in-situ generated bis-CN cobalt A3-triarylcorroles with a tetrabutylammonium counterion. Examples of the synthesized corroles are shown in the figure and represented as [(Ar)3CorCo(CN)]- where (Ar)3Cor is the corrole macrocycle and Ar is one of several meso-phenyl rings containing electron-withdrawing or electron-donating substituents. Figure 1

Halogen Bonding in New Dichloride-Cobalt(II) Complex with Iodo Substituted Chalcone Ligands

The synthesis and properties of new chalcone ligand 4I-L ((2E)-1-[4-(1H-imidazol-1-yl)phenyl]-3-(4-iodophenyl)prop-2-en-1-one) and tetracoordinate Co(II) complex [Co(4I-L)2Cl2], (1a), are reported in this article. Upon recrystallization of 1a, the single crystals of [Co(4I-L)4Cl2]·2DMF·3Et2O (1b) were obtained and crystal structure was determined using X-ray diffraction. The non-covalent interactions in 1b were thoroughly analyzed and special attention was dedicated to interactions formed by the peripheral iodine substituents. The density functional theory (DFT), atoms in molecule (AIM) and noncovalent interaction (NCI) methods and electronic localization function (ELF) calculations were used to investigate halogen bond formed between the iodine functional groups and co-crystallized molecules of diethyl ether.

Novel Phenothiazine-Bridged Porphyrin-(Hetero)aryl dyads: Synthesis, Optical Properties, In Vitro Cytotoxicity and Staining of Human Ovarian Tumor Cell Lines.

We report here the synthetic procedure applied for the preparation of new AB3-type and trans-A2B2 type meso-halogenophenothiazinyl-phenyl-porphyrin derivatives, their metal core complexation and their peripheral modification using Suzuki–Miyaura cross coupling reactions with various (hetero)aryl (phenothiazinyl, 7-formyl-phenothiazinyl, (9-carbazolyl)-phenyl and 4-formyl-phenyl, phenyl) boronic acid derivatives. The meso-phenothiazinyl-phenyl-porphyrin (MPP) dyes family was thus extended by a series of novel phenothiazine-bridged porphyrin-(hetero)aryl dyads characterized by UV–Vis absorption/emission properties typical to the porphyrin chromophore, slightly modulated by increasing the size of peripheral substituents. Three phenothiazine-bridged porphyrin-heteroaryl dyads with fluorescence emission above 655 nm were selected as fluorophores in red spectral region for applications in cellular staining of human ovarian tumors. In vitro experiments of cell metabolic activity displayed a moderate toxicity on human ovarian tumor cell lines (OVCAR-3, cisplatin-sensitive A2780 and cisplatin-resistant A2780cis respectively). Visualization of the stained living cells was performed both by fluorescence microscopy imaging and by fluorescence lifetime imaging under two photon excitation (TPE-FLIM), confirming their cellular uptake and the capability of staining the cell nucleus.

Principal Descriptors of Ionic Liquid Co-catalysts for the Electrochemical Reduction of CO2

Electrochemical reduction of carbon dioxide (CO2RR) is promoted by ionic liquid (IL) co-catalysts, and several mechanisms have been proposed to explain their role. Due to the complexity of the CO2RR and the limited number of active IL co-catalysts, a consensus on the precise role of ILs has not been reached, and it is not possible to improve their activity in a rational way. Herein, we describe guanidinium (Gua) ILs that act as co-catalysts for the CO2RR when employed in non-aqueous electrolytes. The peripheral substituents of the Gua cation were systematically modified allowing the IL co-catalytic properties to be fine-tuned, and on the basis of the observed substitution effects, charge delocalization and availability were shown to be the critical descriptors determining co-catalytic activity. These descriptors can be used to rationalize activity trends for other classes of IL co-catalysts.

Novel Ruthenium Sensitizers Designing for Efficient Light Harvesting under Both Sunlight and Ambient Dim Light

The dye‐sensitized solar cell (DSC) is a proven technology that operates efficiently under both sunlight and ambient dim light. However, because sunlight is significantly different from ambient dim light in terms of irradiance and emission spectrum, designing a single sensitizer that can perform equally efficiently under both conditions remains practically difficult. For the first time, panchromatic Ru(II) sensitizers bearing the tBu substituted 6‐quinolin‐8‐yl‐2,2′‐bipyridine anchor and 2,6‐bis(pyrazolyl)pyridine ancillary with peripheral CF3 and C3F7 substituents and central tBu substituent are synthesized to provide superior conversion efficiency. The quinolin‐8‐yl‐2,2′‐bipyridine anchor enhances the spectrum response from 550 to 700 nm, which is particularly important to fluorescent light spectrum. Furthermore, the introduction of bulky C3F7 and tBu groups effectively increase the steric hindrance that allows better dye uptake and suppresses interfacial recombination, both of which are important for light harvesting under dim light. The champion device in this study exhibits a remarkable power conversion efficiency of 31.82% under 6000 lux fluorescent light without the use of a cosensitizer. Meanwhile, the device also shows a high PCE of 10.37% under simulated 1 sun irradiation, making it the first ruthenium sensitizer suitable for both high and dim light applications under the same fabrication condition in DSC.

Electrochemical and catalytic assessment of peripheral bromoaryl-substituted manganese and iron porphyrazines

The cyclotetramerization reaction following the Linstead approach led to novel symmetrical magnesium(II) aminoporphyrazines with methyl(6-bromo-3-pyridylmethyl) and methyl(4-bromobenzyl) substituents. These products were applied in the demetallation reaction procedure in trifluoroacetic acid in the dark, which resulted in free-base porphyrazine derivatives. Then these macrocycles were remetallated with iron(II) bromide in DMF to give the desired iron(III) porphyrazine macrocycles. Simultaneously, the cyclotetramerization reaction of maleonitrile derivatives with manganese(II) chloride in n-pentanol and DBU led to symmetrical manganese(III) porphyrazines. New porphyrazine complexes with methyl(6-bromo-3-pyridylmethyl) and methyl(4-bromobenzyl) substituents were thoroughly characterized by the use of various analytical techniques, including electronic spectra, mass spectrometry, and FTIR. Macrocycles were subjected to electrochemical and spectroelectrochemical characterization, accompanied by preliminary catalytic study. The electrochemical properties of all obtained macrocycles were assessed with the use of cyclic and differential pulse voltammetry. The electrochemical activity of new macrocycles and their susceptibility to oxidation/reduction processes depended on the presence of nitrogen substituents in their macrocyclic periphery. The electrochemical measurements provided information on the positions of energy levels (HOMO-LUMO) of each porphyrazine, allowing estimation of the electrochemical energy gaps. The calculated electrochemical energy gaps were higher for porphyrazines with methyl(6-bromo-3-pyridylmethyl)amino peripheral substituents than methyl(4-bromobenzyl)amino ones due to the more electronegative nature of nitrogen amine atom. The calculated electrochemical HOMO-LUMO energy level gap values and the optical band gaps were found to agree within approx. 0.2 eV. Iron(III) and manganese(III) porphyrazines were assessed in terms of their catalytic properties. In these studies, DPBF was employed as a substrate of oxidation processes due to its easy UV–vis assessment. The results revealed the catalytic activity of porphyrazines with peripheral methyl(4-bromobenzyl)amino substituents following first-order kinetics.

Synthesis and J-Dimer Formation of Tetrapyrazinoporphyrazines with Different Functional Groups for Potential Biomolecular Probe Applications.

Though tetrapyrazinoporphyrazines (TPyzPzs) are generally presented as universal dark quenchers for oligonucleotide probes, the availability of TPyzPzs bearing different functional groups suitable for attachment to 3', and 5' ends or intrastrand positions remains rather limited. Therefore, a synthetic route to hexa(bis(2-methoxyethyl)amino) or hexa(diethylamino) TPyzPzs functionalized by an azide, hydroxy, or carboxy group or their combinations was developed. Studies of self-assembly into J-dimers in nonpolar solvents and their stability upon titration with pyridine (association constants, KP values, ranging 0.32-12.7×102 M-1 ) revealed that smaller peripheral substituents and functionalization of TPyzPzs improves the stability of J-dimers. ΦΔ and ΦF were low for the monomers (ΦF <0.0001, ΦΔ <0.008, DMF) due to quenching by intramolecular charge transfer; however, they increased in nonpolar solvents and after self-assembly into J-dimer (up to ΦF =0.027, ΦΔ =0.28).

Study of Desorption Products under Laser Irradiation of the Surface of Organic Films

The paper presents the results of mass spectrometric studies of laser-stimulated desorption from the surface of thin films based on organic copper phthalocyanine molecules with peripheral substituents on gallium arsenide substrates. Thin films (30-80 nm) of copper phthalocyanine with peripheral substituents in this regard are studied for the first time. The composition of particles desorbed from the surface of CuPc and CuPcF16 films by laser radiation of various wavelengths of 532 nm and 1.06 μm with a pulse duration of 10 ns was studied. The identification of the main fragments of molecules present in the desorption stream was carried out. It was shown that under the action of laser radiation, the surface is leveled and the films are fragmented, followed by desorption of molecular fragments.

Electrocatalytic hydrogen evolution using triaryl corrole cobalt complex

Three cobalt triaryl corroles bearing an electron‐withdrawing or electron‐donating group at 10‐meso‐phenyl were synthesized and characterized. Two of them are new cobalt corroles prepared in this study. These cobalt corroles were characterized using high‐resolution mass spectrometry, UV–Vis., nuclear magnetic resonance, X‐ray photoelectron spectroscopy, and single‐crystal X‐ray structure determination. All synthesized cobalt corroles efficiently catalyzed the hydrogen evolution reaction (HER) in neutral aqueous media at an overpotential of 838 mV. The HER activity of these cobalt corroles significantly depended on the virtue of peripheral substituents.

Cyclometalated Iridium Bipyridine Complexes with Peripheral Antimony Substituents

As part of our ongoing efforts in the development of main group Lewis acids as anion receptors, we have investigated the synthesis of cyclometalated bipyridine iridium(III) complex decorated by antimony moieties. Reaction of 4‐(diphenylstibino)‐2,2'‐bipyridine (L) with [(ppy)2Ir(μ‐Cl)]2 afforded the corresponding tris‐chelate iridium complex [(ppy)2IrL]+ ([1]+), which was isolated as a hexafluorophosphate salt ([1][PF6]). Reaction of [1][PF6] with excess PhICl2 in DMSO induced the conversion of the diphenylantimony moiety of [1]+ into an anionic diphenyltrichloroantimonate leading to a zwitterionic complex referred to as 2‐Cl. Complexes [1][PF6] and 2‐Cl were characterized by NMR and the structure of 2‐Cl confirmed using X‐ray diffraction. DFT calculations and electrochemical measurments show that the electron‐rich diphenyltrichloroantimonate moiety in 2‐Cl cathodically shifts the Ir(III/IV) redox couple. Luminescence measurements also show that 2‐Cl is less emissive than [1]+.

Aggregation and Molecular Complexation of Bifunctionally Substituted Cobalt Phthalocyaninates in Aqueous Media

The association and extracoordination of water-soluble cobalt complexes with mono- and bifunctionally substituted phthalocyaninates in aqueous solutions with monodentate ligands, such as pyridine and piperidine, were considered. The ability of substituted cobalt phthalocyaninates to coordinate small organic molecules was related to the nature of their peripheral substituents. The type and stability constants of associates formed in aqueous media were determined.

Effects of a Central Atom and Peripheral Substituents on Photoinduced Electron Transfer in the Phthalocyanine–Fullerene Donor–Acceptor Solution-Processable Dyads

For understanding the physical chemistry behind improving photoelectrochemical charge separation parameters and providing solution-processability, multiple peripheral substitution by 3,5-di-tert-bu...

Tribenzoporphyrazines with dendrimeric peripheral substituents and their promising photocytotoxic activity against Staphylococcus aureus

Infectious diseases constitute a serious problem for human health and life. Although many bacterial and fungal infections can be successfully cured by commonly used antibiotics, a new threat emerges in the form of microbial resistance. For this reason, researchers try to find not only new active pharmaceutical ingredients for conventional antibiotherapy but also try to develop new strategies of microbial inactivation. Photodynamic antimicrobial chemotherapy, which relies on reactive oxygen species generated in situ in the presence of a photosensitizer and with the light of an appropriate wavelength, is one of them. Porphyrazines have been considered as potential photosensitizers for anticancer and antimicrobial photodynamic therapy. In this study, three tribenzoporphyrazines with dendrimeric peripheral substituents were subjected to in vitro antimicrobial photocytotoxicity study. One magnesium(II) tribenzoporphyrazine with peripheral 3,5-bis(3,5-dimethoxybenzyloxy)benzylsulfanyl substituents was synthesized and subjected to physicochemical characterization using NMR, UV–Vis, and mass spectrometry techniques. In photochemical studies this molecule revealed moderate singlet oxygen generation ability (ΦΔDMF = 0.12, ΦΔDMSO = 0.13). The other two magnesium(II) tribenzoporphyrazines applied in the biological study were 4-[3,5-di(hydroxymethyl)phenoxy]butylsulfanyl-substituted tribenzoporphyrazine and 4-[3,5-bis(benzyloxy)benzyloxy]phenyl-substituted tribenzopyrazinoporphyrazine. For the assessment, three microbial strains were chosen: Gram-positive bacteria Staphylococcus aureus ATCC 25923, Gram-negative bacteria Escherichia coli ATCC 25922, and fungal strain Candida albicans ATCC 10231. Very high activity against Staphylococcus aureus at low 10-6 M concentration was recorded for magnesium(II) tribenzoporphyrazines with peripheral 3,5-bis(3,5-dimethoxybenzyloxy)benzylsulfanyl and 4-[3,5-di(hydroxymethyl)phenoxy]butylsulfanyl substituents with calculated log reductions of 4.4 and 4.8, respectively. It is worth noting that magnesium(II) tribenzoporphyrazine with 4-[3,5-di(hydroxymethyl)phenoxy]butylsulfanyl substituents revealed also 3.2 log reduction in bacterial growth at the concentration 10-7 M.

Synthesis of nonplanar meso-trifluoromethyl-substituted tetrabenzoporphyrins via oxidation of tetrabutanoporphyrins

Simultaneous synthesis of meso-trifluoromethyl-substituted tetrabutanoporphyrins having one or two trifluoromethyl groups at their 5-, 5,10-, and 5,15-positions has been achieved. The products can be converted into the corresponding meso-trifluoromethyl-substituted tetrabenzoporphyrins by oxidative treatment with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone under reflux. Their crystal structures reveal nonplanar distortion arising from the steric repulsion of the peripheral substituents, which can enhance the solubility of the tetrabenzoporphyrin framework in common solvents without loss of the extended [Formula: see text] conjugation.

Dually directional glycosylated phthalocyanines as extracellular red-emitting fluorescent probes.

The development of new non-aggregated phthalocyanines bearing multivalent saccharide moieties on their macrocyclic rims is of great interest. Many characteristics, including water-solubility, non-toxicity and others, can be feasibly obtained by these amphiphiles which can be considered as a key solution for demonstrating highly efficient photoactive materials in water. Herein, a family of five newly prepared dually directional Zn(ii) containing phthalocyanines (PcG1-4) and azaphthalocyanine (AzaPcG1) glycoconjugates is described. The unique spatial arrangement of the glucoside units based on peripherally hexadeca-(PcG1) and nonperipherally octa-(PcG4) macrocycles provides a fully monomeric behaviour along with a high fluorescence (ΦF∼ 0.21) in aqueous solution. These amphiphiles were characterized by low toxicity, and an extremely low cellular uptake was obtained due to the highly polar nature of the glucoside substituents. Accordingly, their potential as suitable photoactive chromophores for red-emitting extracellular fluorescent probes has been confirmed upon the evaluation of paracellular transport using a layer of MDCKII cells with the permeability coefficient fully comparable with an established evaluator of the integrity of the monolayer.

Boron(iii) β-diketonate-based small molecules for functional non-fullerene polymer solar cells and organic resistive memory devices.

A class of acceptor–donor–acceptor chromophoric small-molecule non-fullerene acceptors, 1–4, with difluoroboron(iii) β-diketonate (BF2bdk) as the electron-accepting moiety has been developed. Through the variation of the central donor unit and the modification on the peripheral substituents of the terminal BF2bdk acceptor unit, their photophysical and electrochemical properties have been systematically studied. Taking advantage of their low-lying lowest unoccupied molecular orbital energy levels (from −3.65 to −3.72 eV) and relatively high electron mobility (7.49 × 10−4 cm2 V−1 s−1), these BF2bdk-based compounds have been employed as non-fullerene acceptors in organic solar cells with maximum power conversion efficiencies of up to 4.31%. Moreover, bistable resistive memory characteristics with charge-trapping mechanisms have been demonstrated in these BF2bdk-based compounds. This work not only demonstrates for the first time the use of a boron(iii) β-diketonate unit in constructing non-fullerene acceptors, but also provides more insights into designing organic materials with multi-functional properties.