Phenoxy Substituents Research Articles

Influence of bulky peripheral substituents on subphthalocyanine derivatives: Implications for photocatalytic and photoelectrochemical hydrogen production

A series of novel subphthalocyanine (SubPc) derivatives with bulky electron-donating substituents were synthesized for visible light-induced photocatalytic and photoelectrochemical hydrogen production. SubPc derivatives were decorated with bulky thiophenoxy (coded SubPc 1–2) and phenoxy (coded SubPc 3–4) substituents to compare the influence of the nature of the peripheral bulky substituents on the photophysical and photocatalytic activity of SubPc. The highest photocatalytic performance was obtained from SubPc 4, having diphenyl phenoxy substituents with an H2 production rate of 7.233 mmol g-1h−1. The photocatalytic hydrogen evolution activities of all SubPc sensitized TiO2 photocatalysts enhanced approximately four times in the presence of Pt co-catalyst. The photocatalysts showed remarkable long-term stability and reproducibility of H2 evolution over 24-hour irradiation. SubPc 4-based photocatalytic system reached a considerable catalytic activity with the H2 production of 16.022 mmol g−1 and a turnover number (TON) value of 34,089 for 24 h irradiation. Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) studies were carried out to better understand the photocatalytic abilities of SubPc derivatives and develop a symbiotic connection with experimental investigations. The results highlight the importance of peripheral substituents in modifying electron density, dipole moment, and HOMO-LUMO energy levels and improving SubPc derivative light-harvesting performance. The presence of 2,6-diisopropyl on SubPc derivatives (SubPc 2 and 4) caused a significant change in the properties, resulting in favourable electron transport characteristics and, therefore, improving photocatalytic performance. Furthermore, the incorporation of TiO2, as shown in SubPc 1@TiO2 and SubPc 2@TiO2, resulted in a modest reduction in chemical hardness, implying increased charge transfer inside the molecule and, as a consequence, enhancing its efficacy as a sensitizer. These theoretical discoveries provide a solid foundation for the customized design and optimization of SubPc derivatives for effective photocatalytic applications.

Chloromanganese and oxo-Titanium (IV) phthalocyanines: Synthesis, electrochemistry and Spectroelectrochemistry

Electrochemical properties of MPcs were determined with electrochemical and in-situ spectroelectrochemical measurements to investigate the influence of the metal center and the number and positions of the substituents. While H2Pc only illustrated Pc based redox processes, the incorporation of TiO2+ and Cl−1-Mn3+ cations into the cavity of Pc ring considerably altered the redox richness of the complexes. Two metal-based reduction couples were observed in addition to the Pc-based processes for both of TiOPc and MnPc. Moreover, altering the number and position of 4-(2-phenylpropan-2-yl)phenoxy substituents slightly influenced the basic redox activity of Pc ring and metal centers. All of these results supported the proposed structure of the complexes. During the redox reactions, pronounced spectral changes were observed with the in situ spectroelectrochemical measurements which caused distinct color changes. Rich redox responses and pronounced spectral and color changes of the complexes indicated their worth as functional material in various electrochemical technologies.

Synthesis and Characterization of New-Type Soluble β-Substituted Zinc Phthalocyanine Derivative of Clofoctol.

In this work, we have described the synthesis and characterization of novel zinc (II) phthalocyanine bearing four 2-(2,4-dichloro-benzyl)-4-(1,1,3,3-tetramethyl-butyl)-phenoxy substituents on the peripheral positions. The compound was characterized by elemental analysis and different spectroscopic techniques, such as FT-IR, 1H NMR, MALDI-TOF, and UV-Vis. The Zn (II) phthalocyanine shows excellent solubility in organic solvents such as dichloromethane (DCM), n-hexane, chloroform, tetrahydrofuran (THF), and toluene. Photochemical and electrochemical characterizations of the complex were performed by UV-Vis, fluorescence spectroscopy, and cyclic voltammetry. Its good solubility allows a direct deposition of this compound as film, which has been tested as a solid-state sensing material in gravimetric chemical sensors for gas detection, and the obtained results indicate its potential for qualitative discrimination and quantitative assessment of various volatile organic compounds, among them methanol, n-hexane, triethylamine (TEA), toluene and DCM, in a wide concentration range.

Organocatalytic Asymmetric Synthesis of Si-Stereogenic Silyl Ethers.

Functionalized enantiopure organosilanes are important building blocks with applications in various fields of chemistry; nevertheless, asymmetric synthetic methods for their preparation are rare. Here we report the first organocatalytic enantioselective synthesis of tertiary silyl ethers possessing “central chirality” on silicon. The reaction proceeds via a desymmetrizing carbon–carbon bond forming silicon–hydrogen exchange reaction of symmetrical bis(methallyl)silanes with phenols using newly developed imidodiphosphorimidate (IDPi) catalysts. A variety of enantiopure silyl ethers was obtained in high yields with good chemo- and enantioselectivities and could be readily derivatized to several useful chiral silicon compounds, leveraging the olefin functionality and the leaving group nature of the phenoxy substituent.

Synthesis of pyrrolyl-BODIPY dyes through regioselective SN Ar reactions and application as a fluorescent sensor for fluoride anion

Two pyrrolyl-BODIPY dyes with 3,5-di-[Formula: see text]-butyl-4-hydroxyphenyl group were synthesized through stepwise S[Formula: see text]Ar reactions of 3,5-dibromoBODIPYs, which were used as a fluorescent sensor for basic anions. The intermediate pyrrolyl-BODIPYs 2a–2b were regioselectively synthesized through an efficient S[Formula: see text]Ar reaction between 3,5-dibromoBODIPY 1a and pyrroles. The target pyrrolyl-BODIPYs 3a–3b with a 3,5-di-[Formula: see text]-butyl-4-hydroxyphenyl group at 3-position and a pyrrole substituent at 5-position were obtained through a second S[Formula: see text]Ar reaction between pyrrolyl-BODIPYs 2a–2b and high steric hindrance 2,6-dibutylphenol in 90% and 88% yields, respectively. In contrast, the reaction between pyrrolyl-BODIPYs 2a–2b and phenol gave pyrrolyl-BODIPYs 3c–3d with phenoxy substituent at 3-position. These pyrrolyl-BODIPYs 3a–2d show strong, sharp absorptions (551–604 nm) and emissions (564–634 nm) with high fluorescence quantum yields up to 0.86 in dichloromethane. Importantly, the 3,5-di-[Formula: see text]-butyl-4-hydroxyphenyl group of pyrrolyl-BODIPY 3a showed a turn-off fluorescent response toward fluoride anion.

Peripherally Crowded Cationic Phthalocyanines as Efficient Photosensitizers for Photodynamic Therapy.

Photodynamic therapy is a treatment modality of cancer based on the production of cytotoxic species upon the light activation of photosensitizers. Zinc phthalocyanine photosensitizers bearing four or eight bulky 2,6-di(pyridin-3-yl)phenoxy substituents were synthesized, and pyridyl moieties were methylated. The quaternized derivatives did not aggregate at all in water and retained their good photophysical properties. High photodynamic activity of these phthalocyanines was demonstrated on HeLa, MCF-7, and EA.hy926 cells with a very low EC50 of 50 nM (for the MCF-7 cell line) upon light activation while maintaining low toxicity in the dark (TC50 ≈ 600 μM), giving thus good phototherapeutic indexes (TC50/EC50) above 1400. The compounds localized primarily in the lysosomes, leading to their rupture after light activation. This induced an apoptotic cell death pathway with secondary necrosis because of extensive and swift damage to the cells. This work demonstrates the importance of a bulky and rigid arrangement of peripheral substituents in the development of photosensitizers.

1-Mono- and 1,7-Disubstituted Perylene Bisimide Dyes with Voluminous Groups at Bay Positions: In Search for Highly Effective Solid-State Fluorescence Materials

A series of 1-mono- and 1,7-disubstituted perylene bisimides (PBIs) with voluminous phenoxy groups at bay positions has been synthesized. These dyes show absorption and emission properties typical for PBIs in solution with high fluorescence quantum yields close to unity. In the solid state, the voluminous substituents at bay positions effectively wrap the dye core and prevent π–π interactions between twofold substituted chromophores. The comparison of UV–vis absorption and fluorescence properties for solutions as well as solid-state thin films, powders, and microcrystals in combination with the respective single-crystal structures allows for establishing the packing structure–optical property relationships. According to this analysis, only with two bulky 2,4,6-tris­(4-tert-butylphenyl)-phenoxy or 2,4,6-tris­(3,5-di-tert-butylphenyl)-phenoxy substituents functionalized PBI chromophores are completely jacketed to afford efficient solid-state emitter materials with fluorescence quantum yields of over 60%. A comparative evaluation of PBIs bearing bulky substituents at imide positions reveals significantly higher solid-state fluorescence quantum yields of the 1,7-substituted PBIs.

Crystal Engineering of 1D Exciton Systems Composed of Single‐ and Double‐Stranded Perylene Bisimide J‐Aggregates

AbstractSingle crystals of three at bay area tetraphenoxy‐substituted perylene bisimide dyes are grown by vacuum sublimation. X‐ray analysis reveals the self‐assembly of these highly twisted perylene bisimides (PBIs) in the solid state via imide–imide hydrogen bonding into hydrogen‐bonded PBI chains. The crystallographic insights disclose that the conformation and sterical congestion imparted by the phenoxy substituents can be controlled by ortho‐substituents. Accordingly, whilst sterically less demanding methyl and isopropyl substituents afford double‐stranded PBI chains of complementary P and M atropo‐enantiomers, single hydrogen‐bonded chains of homochiral PBIs are observed for the sterically more demanding ortho‐phenyl substituents. Investigation of the absorption and fluorescence properties of microcrystals and thin films of these PBIs allow for an unambiguous interpretation of these exciton systems. Thus, the J‐aggregates of the double‐stranded crystals exhibit a much larger (negative) exciton coupling than the single‐stranded one, which in contrast has the higher solid‐state fluorescence quantum yield.

Novel biologically active metallophthalocyanines as promising antioxidant-antibacterial agents: Synthesis, characterization and computational properties

This study reports on the synthesis and characterization of non-peripherally tetrasubstituted zinc(II), copper(II) and cobalt(II) phthalocyanines with 4-(trifluoromethylthio)phenoxy substituents. Synthesized compounds were characterized by FT-IR, 1H NMR, MALDI mass, elemental analysis and UV–Vis spectroscopic methods. By using some parameters obtained from quantum chemical calculations, the activity of the studied ligand (1) against metal atoms was investigated. Based on the obtained results, the NMR, IR and UV–Vis spectra of the ligand (1) in different phases were compared with experimental results. Also, theorical and experimental UV–Vis spectrum values of metallophthalocyanines (2–4) were investigated. Additionally, the possible use of all synthesized metallophthalocyanines for antioxidant and antibacterial agents were investigated. The obtained results showed that CoPc (4) had very good antioxidant activities among others. Although all of the tested metallophthalocyanines (2–4) had some antibacterial activities, ZnPc (2) had the best antibacterial effect against five different bacteria among other metallophthalocyanines tested.

Protein‐like Enwrapped Perylene Bisimide Chromophore as a Bright Microcrystalline Emitter Material

AbstractStrongly emissive solid‐state materials are mandatory components for many emerging optoelectronic technologies, but fluorescence is often quenched in the solid state owing to strong intermolecular interactions. The design of new organic pigments, which retain their optical properties despite their high tendency to crystallize, could overcome such limitations. Herein, we show a new material with monomer‐like absorption and emission profiles as well as fluorescence quantum yields over 90 % in its crystalline solid state. The material was synthesized by attaching two bulky tris(4‐tert‐butylphenyl)phenoxy substituents at the perylene bisimide bay positions. These substituents direct a packing arrangement with full enwrapping of the chromophore and unidirectional chromophore alignment within the crystal lattice to afford optical properties that resemble those of their natural pigment counterparts, in which chromophores are rigidly embedded in protein environments.

Protein-like Enwrapped Perylene Bisimide Chromophore as a Bright Microcrystalline Emitter Material.

Strongly emissive solid‐state materials are mandatory components for many emerging optoelectronic technologies, but fluorescence is often quenched in the solid state owing to strong intermolecular interactions. The design of new organic pigments, which retain their optical properties despite their high tendency to crystallize, could overcome such limitations. Herein, we show a new material with monomer‐like absorption and emission profiles as well as fluorescence quantum yields over 90 % in its crystalline solid state. The material was synthesized by attaching two bulky tris(4‐tert‐butylphenyl)phenoxy substituents at the perylene bisimide bay positions. These substituents direct a packing arrangement with full enwrapping of the chromophore and unidirectional chromophore alignment within the crystal lattice to afford optical properties that resemble those of their natural pigment counterparts, in which chromophores are rigidly embedded in protein environments.

Perylene Bisimide Dyes with up to Five Independently Introduced Substituents: Controlling the Functionalization Pattern and Photophysical Properties Using Regiospecific Bay Substitution.

We report herein a versatile and user-friendly synthetic methodology based on sequential functionalization that enables the synthesis of previously unknown perylene bisimide (PBI) dyes with up to five different substituents attached to the perylene core (e.g., compound 15). The key to the success of our strategy is a highly efficient regiospecific 7-mono- and 7,12-di-phenoxy bay substitution at the “imide-activated” 7- and 12-bay positions of 1,6,7,12-tetrachloroperylene monoimide diester 1. The facile subsequent conversion of the diester groups into an imide group resulted in novel PBIs (e.g., compound 14) with two phenoxy substituents specifically at the 7- and 12-bay positions. This conversion led to the activation of C-1 and C-6 bay positions, and thereafter, the remaining two chlorine atoms were substituted to obtain tetraphenoxy-PBI (compound 15) that has two different imide and three different bay substituents. The methodology provides excellent control over the functionalization pattern, which enables the synthesis of various regioisomeric pairs bearing the same bay substituents. Another important feature of this strategy is the high sensitivity of HOMO–LUMO energies and photoinduced charge transfer toward sequential functionalization. As a result, systematic fluorescence on–off switching has been demonstrated upon subsequent substitution with the electron-donating 4-methoxyphenoxy substituent.

Effect of gold nanoparticle shape on the photophysicochemical properties of sulphur containing metallophthalocyanines

In this work tetrakis–[(thiopheneethoxy) phthalocyaninato] zinc(II) (1), tetrakis–[(thiopheneethoxy) phthalocyaninato] indium (II) chloride (2), tetrakis [(benzo [d]thiazol-2-yl phenoxy) phthalocyaninato] zinc(II) (3), and tetrakis [(benzo [d]thiazol-2-yl phenoxy)phthalocyaninato] indium (II) chloride (4) were linked to both gold nanospheres (AuNSs) and gold nanotriangles (AuNTs) via Au-S and Au-N (the latter for complexes 3 and 4 only) self assembly. The photophysicochemical behaviour of complexes and their conjugates were studied. The conjugates yielded improved triplet and singlet quantum yields, with nanospheres displaying better properties than nanotriangles. The conjugates with a benzothiazole phenoxy substituent also yielded better properties than their thiophene ethoxy counterpart. These conjugates especially those with a benzothiazole phenoxy substituent have potential as photosensitisers for photodynamic therapy applications.

Core-modified of fluoranthene with "propeller" structure for highly sensitive detection of nitroaromatic compounds.

Two fluoranthene derivatives with "propeller" structure, named as 7,8,9,10-tetraphenylfluoranthene (TPFA) and 3-phenoxy-7,8,9,10-tetraphenyl fluoranthene (PO-TPFA), were designed and synthesized by introducing outer phenyl and phenoxy substituents to fluoranthene. Given the steric hindrance of this unique structure, both organic dyes exhibited similar fluorescence spectra and strong fluorescence emission from the solution to the film state. The introduction of a phenoxy group showed obvious influence to the molecular optical properties of fluoranthene. Density functional theory calculations were further conducted to verify this finding. Both dyes were used as fluorescent probes and exhibited and sensitive fluorescence response to nitroaromatic explosives and highly selectivity to picric acid. Furthermore, PO-TPFA exhibited better detection performance to nitroaromatic explosives than TPFA. This work can serve as a guide for molecular fluorescence design because these dyes possess excellent fluorescence in solution and film states and can be used for the sensitive fluorescence detection of nitroaromatic explosives.

η1 -Arene Complexes as Intermediates in the Preparation of Molecular Phosphorescent Iridium(III) Complexes.

Molecular phosphorescent heteroleptic bis-tridentate iridium(III) emitters have been prepared via η1 -arene intermediates. In the presence of 4.0 mol of AgOTf, the complex [(IrCl{κ3 -N,C,N-(pyC6 HMe2 py)})(μ-Cl)]2 (1; pyC6 H2 Me2 py=1,3-di(2-pyridyl)-4,6-dimethylbenzene) reacted with 9-(6-phenylpyridin-2-yl)-9H-carbazole (PhpyCzH) and 2-phenoxy-6-phenylpyridine (PhpyOPh) to give [Ir{κ3 -N,C,N-(pyC6 HMe2 py)}{κ3 -C,N,C'-(C6 H4 pyCzH)}]OTf (2) and [Ir{κ3 -N,C,N-(pyC6 HMe2 py)}{κ3 -C,N,C'-(C6 H4 pyOPh)}]OTf (3). The X-ray diffraction structures of 2 and 3 reveal that the carbazolyl and phenoxy substituents of the C,N,C' ligand coordinate to the metal center to form an η1 -arene π bond. Treatment of 2 and 3 with KOtBu led to the deprotonation of the coordinated carbon atom of the η1 -arene group to afford the molecular phosphorescent [5t+4t'] heteroleptic iridium(III) complexes [Ir{κ3 -N,C,N-(pyC6 HMe2 py)}{κ3 -C,N,C'-(C6 H4 pyCz)}] (4) and [Ir{κ3 -N,C,N-(pyC6 HMe2 py)}{κ3 -C,N,C'-(C6 H4 pyOC6 H4 )}] (5). These complexes are green emitters that display short lifetimes and high quantum yields of 0.73 (4) and 0.87 (5) in the solid state.

Bioinspired flame retardant polymers of tyrosol

ABSTRACTThe enzyme catalyzed polymerization of flame retardant (FR) polymers from the renewable resource 2‐(4‐hydroxyphenyl) ethanol (HPE), commonly known as tyrosol, is presented. The synthesis is environmentally friendly and requires only monomer, peroxidase catalyst, dilute hydrogen peroxide, and deionized water. Phenolic polymers are produced in short, one pot, high yield reactions that require minimal purification. Fourier transform infrared spectroscopy and 1H‐NMR analysis suggest the polymers are coupled through the 1, 2, 4, and 5 positions of the phenol ring and through the phenoxy substituent. Thermogravimetric analysis and pyrolysis combustion flow calorimeter show HPE homopolymers exhibit very low heat release rate and total heat release, while copolymerization with phenol increases already high char yields. Gel permeation chromatography reveals the molecular weight of the polymer increases with ethanol cosolvent concentration. The alcohol cosolvent also increases the proportion of oxyphenylene linkages to the detriment of FR properties. Preliminary quantitative structure–activity relationship toxicity modeling predicts the polymers are negative for developmental toxicity and Ames mutagenicity. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45394.

Coinage Metal Complexes of Phosphonite Analogues of 2‐Diphenylphosphino‐1,1′‐binaphthyl (H‐MOP) and 2‐Diphenylphosphino‐2′‐methoxy‐1,1′‐binaphthyl (MeO‐MOP)

Chiral MOP‐phosphonites containing two phenoxy substituents (S)‐1a/(R)‐1b, a biphenoxy group (S)‐2a/(R)‐2b or the 3,3′‐dimethylbiphenoxy group (S)‐3a/(R)‐3b, have been coordinated to the coinage metals. Six [Au(LP)Cl] complexes have been prepared and five were characterised by X‐ray crystallography, as well as complex [Au{(S)‐3a}2]SbF6. Six [Ag(LP)OTf] complexes were synthesised, studied by VT NMR spectroscopy and, in the case of [Ag{(R)‐2b}OTf], by X‐ray crystallography. Six [Cu(LP)(MeCN)2]PF6 complexes were prepared, and [Cu{(R)‐3b}(MeCN)2]PF6 was characterised crystallographically, as was the decomposition product [Cu{(S)‐1a}(O2PF2)]2.

Synthesis and properties of perylene diimide dyes bearing unsymmetrical and symmetrical phenoxy substituents at bay positions

Perylene diimide dyes bearing symmetrical and unsymmetrical phenoxy substituents at the bay positions (N,N′-diethylhexyl-1-bromo-7-pentafluorophenoxy-substituted perylene diimide and 1,7-diphenoxy-substituted perylene diimide) were prepared. 1H NMR analysis indicated that these compounds contain a small quantity of the 1,6-regioisomer, and yield intramolecular hydrogen bonds. Furthermore, their photophysical, electrochemical, aggregation, and thermal properties were studied. It was found that their photophysical properties, structure, aggregation, and thermal stability in the solid state depend on the structure of the phenoxy substituent.

ω-Phenoxyalkyl substituted bis(indenyl)zirconium dichloride complexes as catalysts for homogeneous ethylene polymerization

Nine bis(indenyl)zirconium dichloride complexes of the type [C9H6-(CH2)n-O-Ar]2ZrCl2 (n=3–5; Ar=Ph, t-Bu-Ph) were synthesized, characterized, activated with methylalumoxane (MAO) and tested for ethylene polymerization. Structure–property-relationship studies showed that the activities of the catalysts depend on the length of the bridging chain between the indenyl and the phenoxy group as well as on the bulk at the phenoxy substituent. A t-Bu substituent at the ortho position of the phenoxy group (5a/MAO) gives a much higher catalyst activity (27,500kgPE/molcath) than the isomer 8a/MAO with a t-Bu substituent at the para position of the phenoxy group (16,700kgPE/molcath). Obviously substituents in the ortho position of the phenyl ring generate a bulkier catalyst cation and this can keep the MAO anion at a further distance to allow easier ethylene coordination and chain growth in the polymerization steps. The mono substituted bis(indenyl) complex (C9H7)[C9H6-(CH2)4-O-4-t-Bu]ZrCl2 shows lower activity (11,700kgPE/molcath) than 8a indicating that the electronic effect is dominating in this type of catalysts.

In silico and pharmacological screenings identify novel serine racemase inhibitors

d-Serine is a coagonist of the N-methyl-d-aspartate (NMDA)-type glutamate receptor and its biosynthesis is catalyzed by serine racemase (SR). The overactivation of the NMDA receptor has been implicated in the development of neurodegenerative diseases, strokes, and epileptic seizures, thus, the inhibitors of SR have potential against these pathological states. Here, we have developed novel inhibitors of SR by in silico screening and in vitro enzyme assay. The newly developed inhibitors have lower IC50 value comparing with that of malonate, one of the standard SR inhibitor. The structural features of novel inhibitors suggest the importance of central amide structure having a phenoxy substituent in their structure for the SR inhibitory activity. The present findings suggest the importance and rational development of new drugs for diseases of NMDAR overactivation.