Phthalocyanine Periphery Research Articles

The effect of phthalocyanine's periphery on the biological activities of carbazole-containing metal phthalocyanines.

This study reports the synthesis and characterization of two new mono- and di-substituted phthalonitriles namely 4-((9H-carbazol-3-yl)oxy)-5-chlorophthalonitrile and 4,5-bis((9H-carbazol-3-yl)oxy)phthalonitrile, respectively. Cyclotetramerization of the new phthalonitriles in the presence of zinc(II) acetate resulted in related zinc(II) phthalocyanines. To study the effect of the position and number of substituents on the biological properties of the phthalocyanines, peripherally or non-peripherally tetra-substituted zinc(II) phthalocyanines bearing (9H-carbazol-3-yl)oxy groups, as well as axially di-substituted silicon phthalocyanines containing the same groups, were prepared. Since gold nanoparticles are well-known as efficient drug delivery agents, the surface of these metal nanoparticles was functionalized with all the compounds. This modification also improved the solubility of the phthalocyanines in aqueous media. In this study, the antioxidant, DNA cleavage, and toxic/phototoxic activities of the resultant nanoconjugates were examined. With a combination of metal ion and substituent (nature, number, and position) effects, the silicon(IV) phthalocyanine exhibited the highest biological properties.

Synthesis and Properties of Tetra[4,5](2,4,5-Trichlorophenoxy)Phthalocyanine Metal Complexes

n order to study the effect of phthalocyanine periphery modification by halogens on spectral and other properties of phthalocyanine derivatives, the synthesis of cobalt, nickel and copper complexes of tetrakis[4,5](2,4,5-trichlorophenoxy)phthalocyanine was carried out by the "nitrilic" method using 4,5-di(2,4,5-trichlorophenoxy)phthalonitrile and corresponding metal acetates on heating at 180–200 °C. All compound structures were confirmed by elemental analysis, MALDI-TOF spectrometry, IR and electronic absorption spectroscopy. The ability of the synthesised metallophthalocyanines to dissolve in concentrated sulfuric acid, dimethylformamide, and chloroform was investigated. The effect of metal on the position of the Q band in elect-ronic absorption spectra of synthesized compounds is studied. The possibility of the synthesized phthalocyanine metal complexes to manifest mesomorphism characteristic of discotic mesogens was evaluated. According to the performed mesomorphism prediction, the studied compounds are unable to form mesomorphic state of the specified type. These theoretical calculations are in a good agreement with the experimental data (the coincidence is 100 %).

Crown-ether-substituted asymmetric phthalocyanine derivatives/CdS self-assembled hybrid films with an unprecedented high response toward NO2

Two asymmetrical amphiphilic phthalocyanines simultaneously containing hydrophobic alkoxy and hydrophilic 15-crown-5-ether substituents at the phthalocyanine periphery H2{Pc(15C5)3[(OC8H[Formula: see text]]}(Pc-1) and H2{Pc(15C5)[(OC8H[Formula: see text]]}(Pc-2) and their symmetrical analogue H2[Pc(OC8H[Formula: see text]] (Pc-3) have been synthesized and characterized. The Pc-n/CdS ([Formula: see text] 1, 2 and 3, respectively) hybrid films are obtained successfully via a simple quasi-Langmuir–Shäfer (QLS) method using H2S-vapor annealing over the Pc-n/Cd[Formula: see text] self-assembled film formed at the interface of the air/CdCl2 aqueous solution. The film-structure and properties of both the hybrid Pc-n/CdS and pure Pc-n films are comparatively studied by a wide range of methods including UV-vis, polarized UV-vis, XRD, SEM and I–V measurements. Experimental results exhibit a slipped co-facial stacking mode in an “edge-on” conformation ([Formula: see text]-type aggregate) formed for the phthalocyanine molecules in both pure Pc-n films and the corresponding Pc-n/CdS hybrid films, with increasing intermolecular [Formula: see text]–[Formula: see text] interactions in the order of Pc-n <Pc-n/CdS and Pc-3/CdS <Pc-2/CdS <Pc-1/CdS, respectively. Accordingly, film-microstructures, crystallinity and conductivity are effectively improved by introducing CdS nanoparticles into the 15-crown-5-substituented phthalocyanines forming Pc-1/CdS and Pc-2/CdS hybrid films. These render excellent sensing performance towards NO2 in the 0.05–2.5 ppm range within a fast dynamic exposure period of 30 s. Strikingly, Pc-1/CdS hybrid film presents an unprecedented high sensitivity of 157.3%.ppm[Formula: see text] vs. very low NO2 concentration range of 0.05˜0.25 ppm, achieving one of the best room temperature sensing performances in terms of high sensitivity, rapid responsibility and low detection limit among self-assembled film-based NO2 sensors.

Photodynamic inactivation of Enterococcus faecalis by non-peripherally substituted magnesium phthalocyanines entrapped in lipid vesicles

Photophysical properties and photodynamic antibacterial potential of magnesium phthalocyanines bearing 2-propoxy, benzyloxy, 3,5-bis(benzyloxy)benzyloxy substituents at non-peripheral positions were studied. The UV–Vis absorption spectra of researched phthalocyanine derivatives were found typical. Extension of peripheral substituent size from 2-propoxy to benzyloxy and finally 3,5-bis(benzyloxy)benzyloxy was accompanied by the rise of quantum yield of fluorescence up to 0.17 and 0.04 in DMF and DMSO, respectively. Similarly, the expansion of the phthalocyanine periphery from the 2-propoxy to benzyloxy and 3,5-bis(benzyloxy)benzyloxy groups resulted in a detectable increase of the singlet oxygen quantum yield values to 0.04, 0.12, 0.14 respectively, which was assessed following direct method of singlet oxygen phosphorescence measurement at 1270 nm. Studied phthalocyanines undergo photobleaching process with the quantum yields at the level of 10−6 in DMSO and 10−5 in DMF. The size of phthalocyanine impacted the process of liposomal formulation. Small liposome vesicles containing non-peripherally substituted phthalocyanines with 2-propoxy and benzyloxy substituents were obtained following extrusion method. The unification process of the liposomes loaded with 3,5-bis(benzyloxy)benzyloxy non-peripherally substituted phthalocyanines was not possible. In in vitro antimicrobial photodynamic inactivation study, log reduction values of bacterial (Enterococcus faecalis) growth at 3.61 and 2.99 were achieved for liposomal formulations containing phthalocyanines with 2-propoxy and benzyloxy substituents respectively, whereas phthalocyanine with 3,5-bis(benzyloxy)benzyloxy substituents was inactive. Phthalocyanine with 2-propoxy substituents exhibited relatively low toxicity in Vibrio fischeri bioluminescence test, whereas phthalocyanine with benzyloxy substituents revealed intense bioluminescence, which could be associated with hormesis phenomenon.

Polymorphism in the self-assembled nanostructures of a tris(phthalocyaninato) europium derivative: Phase-dependent semiconducting and NO2 sensing behaviour

A new trifluoroethoxy-substituented tris(phthalocyaninato) europium complex Eu2[Pc(OCH2CF3)4]3 {[Pc(OCH2CF3)4] = 2(3),9(10),16(17),23(24)-tetrakis(2,2,2-trifluoroethoxy)phthalocyaninate}, is designed and synthesized. Introduction of trifluoroethoxy substituents at the phthalocyanine periphery within the triple-decker complex ensures their good solubility in conventional organic solvents. Significantly, depending on the fluorine-participated multiple hydrogen bonding and the π–π interactions in different solvent systems (i.e. n-hexane and water), the self-assembly of the Eu2[Pc(OCH2CF3)4]3 molecules results in well controlled morphologies (nano-bowling bowls, nanobelts and nano-particles) with totally different phases (χ, β and α phases). Furthermore, the sensitivity to NO2 at varied concentrations in the range of 20–1600 ppb, follows the order of nano-bowling bowls in χ phase (SA-1) » nanobelts in β phase (SA-2) > nano-particles in α phase (SA-3), revealing the effect of both phase structure and morphology on sensing performance of the Eu2[Pc(OCH2CF3)4]3. In particular, SA-1 displays unexpected high percent current change of 6.52% to NO2 gas as low as 20 ppb at room temperature, representing thus far the best result of the room-temperature NO2 gas sensing performance in terms of the lowest detection limit with largest response. The present work not only represents the first observation of χ, β and α polymorphs for the sandwich-type triple-decker tetrapyrrole-based rare earth complexes, but more importantly provides an efficient strategy to obtain high performance organic semiconductor-based gas sensors through molecular design and solvent-triggered phase transformations.

H-aggregation mode in triple-decker phthalocyaninato-europium semiconductors. Materials design for high-performance air-stable ambipolar organic thin film transistors

Two new tris(phthalocyaninato) europium complexes Eu2(Pc)[Pc(OPh)8]2 (1) and Eu2[Pc(OPh)8]3 (2) [Pc=unsubstituted phthalocyaninate; Pc(OPh)8=2,3,9,10,16,17,23,24-octaphenoxyphthalocyaninate], were designed and synthesized. Introduction of different number of electron-withdrawing phenoxy substituents at the phthalocyanine periphery within the triple-decker complexes not only ensures their good solubility in conventional organic solvents, but more importantly successfully tunes their HOMO and LUMO levels into the range of air-stable ambipolar organic semiconductor required on the basis of electrochemical studies over both 1 and 2, meanwhile fine controlling of aggregation mode (H vs. J) in solution-based film for improving OTFT performance is also achieved. Measurements over the OTFT devices fabricated from these sandwich compounds by a solution-based quasi–Langmuir–Shäfer (QLS) method reveal their ambipolar semiconductor nature associated with suitable HOMO and LUMO energy levels. Due to the H-aggregation mode employed by the heteroleptic triple-decker molecules in the QLS film, excellent performances with the electron and hole mobility in air as high as 0.68 and 0.014cm2V−1s−1, respectively, have been revealed for the OTFT devices of heteroleptic triple-decker 1. This represents the best performance so far for solution-processable ambipolar single-component phthalocyanine-based OTFTs obtained under ambient conditions. In good contrast, homoleptic analogue 2 prefers to J-type aggregation and this results in relatively lower electron and hole mobility, around 0.041 and 0.0026cm2V−1s−1 in air, respectively, for the devices fabricated. In particular, the performance of the devices fabricated based on 1 was found to remain almost unchanged in terms of both the carrier mobilities and on/off ratio even after being stored under ambient for 4months.

Tuning the semiconducting nature of bis(phthalocyaninato) holmium complexes via peripheral substituents

The semiconducting properties of the heteroleptic and homoleptic bis(phthalocyaninato) holmium complexes bearing electron-withdrawing phenoxy substituents at the phthalocyanine periphery, namely Ho(Pc)[Pc(OPh)8] (1) and Ho[Pc(OPh)8]2 (2) [Pc = unsubstituted phthalocyaninate; Pc(OPh)8 = 2,3,9,10,16,17,23,24-octaphenoxyphthalocyaninate] have been investigated comparatively. Using a solution-based Quasi–Langmuir–Shafer (QLS) method, the thin solid films of the two compounds were fabricated. The structure and properties of the thin films were investigated by UV-vis absorption spectra, X-ray diffraction (XRD) and atomic force microscopy (AFM). Experimental results indicated that H-type molecular stacking mode with the common preferential molecular “edge-on” orientation relative to the substrate has been formed, and the intermolecular face-to-face π–π interaction and film microstructures are effectively improve by increasing the number of phenoxy substituents of the Pc periphery within the double-decker complexes. The electrical conductivity of Ho(Pc)[Pc(OPh)8] films was measured to be approximately 4 orders of magnitude larger than that of Ho[Pc(OPh)8]2 films, indicating significant effect of peripheral electron-withdrawing phenoxy groups on conducting behaviour of bis(phthalocyaninato) holmium complexes. In addition, the gas sensing behaviour of the QLS films of 1 and 2 toward electron donating gas, NH3, was investigated in the concentration range of 15–800 ppm. Surprisingly, contrary responses towards NH3 were found for the QLS films of 1 and 2. In the presence of NH3, the conductivity of the films of Ho(Pc)[Pc(OPh)8] (1) decreased while the conductivity of the films of Ho[Pc(OPh)8]2 (2) increased. This observation clearly demonstrated the p- and n-type semiconducting nature for 1 and 2, respectively. Furthermore, compared to the heteroleptic 1 having a hole mobility of 1.7 × 10−4 cm2 V−1 s−1, homoleptic 2 exhibits an electron mobility as high as 0.54 cm2 V−1 s−1. Therefore, the inversion of the semiconducting nature of the double-deckers from p- to n-type can be successfully and easily realized just by increasing the number of peripheral phenoxy groups attached to the conjugated Pc cores.

Designing nickel phthalocyanine periphery by alkyl chain via [1,3,4]-oxadiazole

Nickel phthalocyanine (NiPc, 1) periphery has been decorated by alkyl chains of varying chain length via [1,3,4]-oxadiazole moiety (NiPcs 3a–3f). All the newly synthesized compounds NiPcs 3a–3d have been completely characterized by elemental analysis, FT-IR, solid-state UV-Vis, and solid-state 13C NMR spectroscopy, in addition to X-ray diffraction, scanning electron microscopy, and thermal analysis. The effect of chain length in the NiPc periphery on electronic absorption and DC electrical conductivity has been investigated.

The first solution-processable n-type phthalocyaninato copper semiconductor: tuning the semiconducting nature via peripheral electron-withdrawing octyloxycarbonyl substituents

A series of unsymmetrical phthalocyaninato copper complexes simultaneously incorporating electron-withdrawing and electron-donating substituents at the phthalocyanine periphery Cu{Pc(15C5)[(COOC8H17)6]} (2), Cu{Pc[(adj-15C5)2][(COOC8H17)4]} (3), Cu{Pc[(opp-15C5)2][(COOC8H17)4]} (4), Cu{Pc(15C5)3[(COOC8H17)2]} (5) were prepared and isolated. For comparative studies, symmetrical analogues including 2,3,9,10,16,17,24,25-octakis(octyloxycarbonyl)phthalocyaninato copper complex Cu[Pc(COOC8H17)8] (1) and 2,3,9,10,16,17,24,25-tetrakis(15-crown-5)phthalocyaninato copper complex Cu[Pc(15C5)4] (6) were also prepared. Their electrochemistry was studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). With the help of a solution-based self-assembly process, these compounds were fabricated into organic field effect transistors (OFETs) with top contact configuration on hexamethyldisilazane (HMDS)-treated SiO2/Si substrate. In line with the electrochemical investigation results, a p-type OFET with a carrier mobility (for holes) of 0.06 cm2 V−1 s−1 was shown for Cu[Pc(15C5)4] (6) with electron-donating 15-crown-5 as the sole type of peripheral substituent. In contrast, n-type devices with a carrier mobility (for electrons) of 6.7 × 10−6–1.6 × 10−4 cm2 V−1 s−1 were achieved for 1–5 with electron-withdrawing octyloxycarbonyl substituents at the peripheral positions of phthalocyanine ring, indicating the significant effect of electron-withdrawing octyloxycarbonyl substituents on tuning the nature of phthalocyanine organic semiconductors. The present results represent the first example of solution-processed n-type phthalocyanine-based OFET devices.

Decorating nickel phthalocyanine periphery by aryl-1,3,4-oxadiazole pendants: synthesis, characterization, and conductivity studies

We have decorated nickel phthalocyanine (NiPc) periphery by four different aryl-[1,3,4]-oxadiazole pendants. Introduction of aryl-[1,3,4]-oxadiazole pendants into the NiPc core results in improved thermal stability, fine-tuning of the position of the Q-band with decrease in band gap, indicating effective electronic communication between the two different ring systems with NiPc core. The magnitude of DC electrical conductivity for aryl-[1,3,4]-oxadiazole-substituted NiPcs 3a–3d is found to be ∼105 times higher than the parent NiPc (1). The temperature-dependent DC conductivity studies reveal semiconducting nature of the newly synthesized NiPc compounds with significant decrease in thermal activation energy (ΔE) compared to parent NiPc.