Redox and Photoinduced Electron-Transfer Properties in Short Distance Organoboryl Ferrocene-Subphthalocyanine Dyads

Preparation and Optical and Electrochemical Properties of Boron (III) Octafluorosubphthalocyanines with One Triselenole and One Diselenet Ring

Unsymmetric boron (III) subphthalocyanines with a triselenole ring or a diselenete ring and eight fluoro groups were prepared by the reaction of 5,6-dicyano-4,7-diethylbenzo-[1,2,3]triselenole and tetrafluorophthalonitrile with trichloroborane in xylene. The reaction was accompanied by a contraction of the triselenole ring to the diselenete ring. The substrate, dicyanobenzo[1,2,3]triselenole, was prepared by a new procedure via a photolytic demethylenation reaction of 3,7-diethyl[1,3]diselenolophthalonitrile using a 10 W white LED light. While triselenolosubphthalocyanine was treated by triphenylphosphine to give the diselenete derivative, the reaction of diselenetosubphthalocyanine with Woolion's reagent produced the expanded triselenole ring. The diselenete derivative reacted with tetrakis(triphenylphosphine)platinum to yield the corresponding platinum complex with Se-Pt bonds. Q-band absorption for the products appeared at around λmax=590 nm in the UV-vis spectrum and weak emission was observed at about λe=620 nm. When diselenetosubphthalocyanine was treated with pentachloro antimonate in dichloromethane or sodium metal in hexane/tetrahydrofuran, the solution showed strong ESR signals. The structures of model compounds were optimized using the DFT method with the Gaussian 09 program at the B3LYP/6-31G (d, p) level.

High-Spin State of a Ferrocene Electron Donor Revealed by Optical and X-ray Transient Absorption Spectroscopy

Ferrocene is one of the most common electron donors, and mapping its ligand-field excited states is critical to designing donor-acceptor (D-A) molecules with long-lived charge transfer states. Although 3(d-d) states are commonly invoked in the photophysics of ferrocene complexes, mention of the high-spin 5(d-d) state is scarce. Here, we provide clear evidence of 5(d-d) formation in a bimetallic D-A molecule, ferrocenyl cobaltocenium hexafluorophosphate ([FcCc]PF6). Femtosecond optical transient absorption (OTA) spectroscopy reveals two distinct electronic excited states with 30 and 500 ps lifetimes. Using a combination of ultraviolet, visible, near-infrared, and short-wave infrared probe pulses, we capture the spectral features of these states over an ultrabroadband range spanning 320 to 2200 nm. Time-dependent density functional theory (DFT) calculations of the lowest triplet and quintet states, both primarily Fe(II) (d-d) in character, qualitatively agree with the experimental OTA spectra, allowing us to assign the 30 ps state as the 3(d-d) state and the 500 ps state as the high-spin 5(d-d) state. To confirm the ferrocene-centered high-spin character of the 500 ps state, we performed X-ray transient absorption (XTA) spectroscopy at the Fe and Co K edges. The Fe K-edge XTA spectrum at 150 ps shows a red shift of the absorption edge that is consistent with an Fe(II) high-spin state, as supported by ab initio calculations. The transient signal detected at the Co K-edge is 50× weaker, confirming the ferrocene-centered character of the excited state. Fitting of the transient extended X-ray absorption fine structure region yields an Fe-C bond length increase of 0.25 ± 0.1 Å in the excited state, as expected for the high-spin state based on DFT. Altogether, these results demonstrate that the high-spin state of ferrocene should be considered when designing donor-acceptor assemblies for photocatalysis and photovoltaics.

Cationic Axial Ligand Effects on Sulfur-Substituted Subphthalocyanines

Herein, we report the synthesis of sulfur-substituted boron(III) subphthalocyanines (SubPcs) with cationic axial ligands. Subphthalocyanines were synthesized by a condensation reaction using the corresponding phthalonitriles and boron trichloride as a template. An aminoalkyl group was introduced on the central boron atom; this process was followed by N-methylation to introduce a cationic axial ligand. The peripheral sulfur groups shifted the Q band of SubPcs to a longer wavelength. The cationic axial ligands increased the polarity and enhanced the hydrophilicity of SubPcs. The effect of axial ligands on absorption and fluorescence properties is generally small. However, a further red shift was observed by introducing cationic axial ligands into the sulfur-substituted SubPcs. This change is similar to that in sulfur-substituted silicon(IV) phthalocyanines. The unique effect of the cationic axial ligand was extensively investigated by theoretical calculations and electrochemistry. In particular, the precise oxidation potential was determined using ionization potential measurements. Thus, the results of the present study provide a novel strategy for developing functional dyes and pigments based on SubPcs.

Recent advances in subphthalocyanines and related subporphyrinoids

Subporphyrinoids constitute a class of extremely versatile and attractive compounds. Herein, a comprehensive review of the most recent advances in the fundamentals and applications of these cone-shaped aromatic macrocycles is presented.

Red-light-activatable ruthenium phthalocyanine catalysts

Phthalocyanine ruthenium complexes were identified as red-light activatable catalysts for trifluoromethylation reactions. The red-light mediated chlorotrifluoromethylation of alkenes could proceed without any sacrificial reducing reagents. This reaction exhibited good compatibility with a blue-light-absorbing substrate, while under irradiation with blue light, i.e., under traditional photoreaction conditions, this substrate decomposed completely.

Synthesis, Characterization and Optoelectronic Property of Axial-Substituted Subphthalocyanines

Two novel substituted subphthalocyanines have been prepared introducing m-hydroxybenzoic acid and m-hydroxyphenylacetic acid into the axial position of bromo-subphthalocyanine. The compounds have been characterized by Fourier transform infrared (FT-IR), Nuclear Magnetic Resonance (NMR) and single-crystal X-rays diffraction (XRD) methods. Their photophysical properties show that the axial substitution results into a relatively higher fluorescence quantum efficiency (ΦF=5.74 for m-hydroxybenzoic acid and 9.09 % for m-hydroxyphenylacetic acid) in comparison with that of the prototype compound, despite the almost negligible influence on the maximum absorption or the emission position. Moreover, the electrochemical behaviors show that the axial-substituted subphthalocyanines also exhibit enhanced specific capacitances of 395 F/g (m-hydroxybenzoic acid) and 362 F/g (m-hydroxyphenylacetic acid) compared with 342 F/g (the prototype) to the largest capacitance at the scan rate of 5 mV/s, and the significantly larger capacitance retentions of 83.6 % and 82.1 % versus 37.3 % upon density up to 3 A/g. These results show the potential of these axial-substituted subphthalocyanines in the use as organic photovoltaics and supercapacitors.

Electrochemical data of ferrocenylsubphthalocyanine dyads

The data presented in this paper is related to the research article entitled “Synthesis, Spectroscopy, Electrochemistry and DFT of Electron-Rich Ferrocenylsubphthalocyanines” [1] where electrochemical redox data and cyclic voltammograms at only a scan rate of 0.10 V s⁻¹ of four ferrocenylsubphthalocyanine dyads Fc(CH₂)_nCO₂BSubPc(H)₁₂ (n = 0, 1 or 3) and FcCO(CH₂)₂CO₂BSubPc(H)₁₂, are presented. This data article provides extensive electrochemical redox data and cyclic voltammograms at various scan rates from 0.05 up to 5.00 V s⁻¹ to illustrate the effect of the different scan rates on the electrochemical behaviour of the four ferrocenylsubphthalocyanine dyads.

Oxidation and reduction data of four subphthalocyanines with axially coordinated ferrocenylcarboxylic acids

Redox data obtained from cyclic voltammetry experiments of the Fe^II/III and ring-based oxidation and reductions of subphthalocyanines containing a ferrocenylcarboxylic acid as axial ligand, is presented in this data in brief article. The Fe^II/III oxidation of ferrocenylsubphthalocyanines which containing the electron-withdrawing fluorine atoms at the peripheral and non-peripheral positions, are ca. 0.100 V more positive than Fe^II/III oxidation of ferrocenylsubphthalocyanines containing hydrogens at the peripheral and non-peripheral positions. For more insight into the reported data, see the related research article “Redox and photophysical properties of four subphthalocyanines containing ferrocenylcarboxylic acid as axial ligands” [1].

Synthesis, Spectroscopy, Electrochemistry and DFT of Electron-Rich Ferrocenylsubphthalocyanines

A series of novel ferrocenylsubphthalocyanine dyads Y-BSubPc(H)₁₂ with ferrocenyl-carboxylic acids Y-H = (FcCH₂CO₂-H), (Fc(CH₂)₃CO₂-H) or (FcCO(CH₂)₂CO₂-H) in the axial position were synthesized from the parent Cl-BSubPc(H)₁₂ via an activated triflate-SubPc intermediate. UV/Vis data revealed that the axial ferrocenyl-containing ligand did not influence the Q-band maxima compared to Cl-BSubPc(H)₁₂. A combined electrochemical and density functional theory (DFT) study showed that Fe group of the ferrocenyl-containing axial ligand is involved in the first reversible oxidation process, followed by a second oxidation localized on the macrocycle of the subphthalocyanine. Both observed reductions were ring-based. It was found that the novel Fc(CH₂)₃CO₂BSubPc(H)₁₂ exhibited the lowest first macrocycle-based reduction potential (-1.871 V vs. Fc/Fc⁺) reported for SubPcs till date. The oxidation and reduction values of Fc(CH₂)_nCO₂BSubPc(H)₁₂ (n = 0-3), FcCO(CH₂)₂CO₂BSubPc(H)₁₂, and Cl-BSubPc(H)₁₂ illustrated the electronic influence of the carboxyl group, the different alkyl chains and the ferrocenyl group in the axial ligand on the ring-based oxidation and reduction values of the SubPcs.

Redox and Photophysical Properties of Four Subphthalocyanines Containing Ferrocenylcarboxylic Acid as Axial Ligands

Four new ferrocenylsubphthalocyanines Y-BSubPc, with ferrocenylcarboxylic acid YH = Fc-CH₂-CH₂-COOH (1) or Fc-CH═CH-COOH (2) in the axial Y position, were synthesized with a 40% yield. The axial ferrocenylcarboxylic acid moiety did not have a significant influence on the position of the Q bands maxima of the UV/vis spectra of the ferrocenylsubphthalocyanines or on the ¹H NMR position of the ring proton peaks of Y-BSubPc(H₁₂) or on the ¹⁹F NMR position of the ring F peaks of YSubPc(F₁₂), relative to their respective parent compounds Cl-BSubPc(H₁₂) 3 and Cl-BSubPc(F₁₂) 4, containing axial chlorine. Very weak metal-to-ligand-charge-transfer bands (MLCT) in the near-IR region were observed. An electrochemical study utilizing cyclic voltammetry showed that electronic communication exists between ferrocene on the axial ferrocenylcarboxylic acid and the π-electrons of the macrocycle of the ferrocenylsubphthalocyanine (Fc(CH₂)₂COO)-BSubPc(H)₁₂,5, (Fc(CH)₂COO)-BSubPc(H)₁₂, 6, (Fc(CH₂)₂COO)-BSubPc(F)₁₂, 7, and (Fc(CH)₂COO)-BSubPc(F)₁₂, 8. The Fe group of the ferrocenyl-containing axial ligand is involved in the first reversible oxidation process, followed by a second oxidation localized on the subphthalocyanine ligand. The fluorine ring substituents in SubPcs 7 and 8 caused the ferrocenyl oxidation to shift more positive by ca. 0.1 V, compared to SubPcs 5 and 6 without fluorine. Density functional theory (DFT) calculations provided further insight into the properties of these novel ferrocenylsubphthalocyanines. The neutral species of SubPcs 5-8 have LUMOs with mainly π-ring character and HOMOs with mainly iron-d character, confirming ring-based reduction, metal-based Fe(II) to Fe(III) oxidation, as well as weak MLCT in the near-IR region. Further DFT optimization of the cation (oxidized) species was essential to verify the second ring-based oxidation.

A theoretical study on electronic spectra of a novel series of metal substituted boron subphthalocyanine chloride

Boron subphthalocyanine chloride has been extensively studied by experimentalists and computational chemists due to its unique optical and electronic properties. It has been practical to modify the optical and physical properties of subphthalocyanine through axial, peripheral, and center substitutions or ring expansion. However, there have been few investigations on the substitution of central boron atom. In the present work, a new metal-substituted (center substitution of boron atom) series of boron subphthalocyanine chloride (metal = Fe, Co, Ni, Cu, and Zn) are theoretically designed utilizing modern density functional theory. The optimized results of this series in gas phase and with polarizable continuum model show that they may be chemically stable, and the predicted order of the stability of MSubPC is Fe>Cu>Ni>Co>Zn. Also, this new series of MSubPC molecules all becomes more non-planar and has much smaller dipole moments, which imply that they may be feasible for blend with organic acceptors. The HOMO-LUMO energy gaps of MSubPC (M=Co, Ni, Cu) are smaller than that of subPC. Furthermore, the wavelength of simulated absorption peaks of ZnSubPC and NiSubPC is red-shifted with respect to prototype subPC molecule in the visible region, and FeSubPC has noticeably stronger absorption strength than subPC because its excitation involves more orbital transitions and d electrons. The work here shows a new way to design photoelectric materials based on subphthalocyanine with center metal substitution.

Tri- and hexaferrocenyl-substituted subphthalocyanines in the quest for the optimum electron donor–acceptor distances

Three and six ferrocenyl subunits have been attached to the periphery of subphthalocyanines (SubPcs).

Ferrocene–BODIPYmerocyanine dyads: new NIR absorbing platforms with optical properties susceptible to protonation

Ferrocene–BODIPYmerocyanine dyads 5 and 6 were synthesized and characterized by spectroscopy, electrochemistry, and DFT calculations.

A novel hybrid blend based on phenoxy-substituted boron subphthalocyanine for organic photodetectors

Phenoxy-substituted boron subphthalocyanine, blended with a conductive polymer MEH-PPV, is presented as a photoresistive organic material. Using an easily accessible drop casting technique, the blend produces a thin-layer organic photoresistor with a photoresistive ratio of ~2–12. Variations in the blend composition and morphology are shown to change the transport properties of the material. The photoelectrochemical characteristics of the photoresistor are discussed in terms of impedance spectroscopy and the morphology of the material is analyzed using confocal fluorescent microscopy. The device developed is a daylight detector.