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.

Analysis of the Solvent Effects on the Crystal Growth of Peripherally Chlorinated Boron Subphthalocyanines

We report the characterization of the crystal/nano-structures for hexachloro-boron subphthalocyanines (Cl6BsubPc) grown via a variety of solvent diffusion methods and also with having axial substitutions variants: chloride; phenoxy; naphthoxy and...

Fully Conjugated Pyrene-BODIPY and Pyrene-BODIPY-Ferrocene Dyads and Triads: Synthesis, Characterization, and Selective Noncovalent Interactions with Nanocarbon Materials

Several pyrene-boron-dipyrromethene (BODIPY) and pyrene-BODIPY-ferrocene derivatives with a fully conjugated pyrene fragment appended to the α-position(s) of the BODIPY core have been prepared by Knoevenagel condensation reaction and characterized by one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR), UV-vis, fluorescence spectroscopy, high-resolution mass spectrometry as well as X-ray crystallography. The redox properties of new donor-acceptor BODIPY dyads and triads were studied by electrochemical (cyclic voltammetry (CV) and differential pulse voltammetry (DPV)) and spectroelectrochemical approaches. Formation of weakly bonded noncovalent complexes between the new pyrene-BODIPYs and nanocarbon materials (C₆₀, C₇₀, single-walled carbon nanotube (SWCNT), and graphene) was studied by UV-vis, steady-state fluorescent, and time-resolved transient absorption spectroscopy. UV-vis and fluorescent spectroscopy are indicative of the much stronger and selective interaction between new dyes and (6,5)-SWCNT as well as graphene compared to that of C₆₀ and C₇₀ fullerenes. In agreement with these data, transient absorption spectroscopy provided no evidence for any significant change in excited-state lifetime or photoinduced charge transfer between pyrene-BODIPYs and C₆₀ or C₇₀ fullerenes when the pyrene-BODIPY chromophores were excited into the lowest-energy singlet excited state. Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations suggest that the pyrene fragments are fully conjugated into the π-system of BODIPY core, which correlates well with the experimental data.

Reaction of GaIIIClPc, SnIVCl2TPP and BIIIClSubPc with cyanide anions: reduction of macrocycles vs. formation of cyano-containing macrocyclic anions

The reaction of GaIIIClPc, SnIVCl2TPP and BIIIClSubPc containing phthalocyanine (Pc), tetraphenylporphyrin (TPP) and subphthalocyanine (SubPc) macrocycles with cyanide in the presence of cryptand[2.2.2] under anaerobic conditions yields crystalline salts in which cyano anions substitute chloride anions at GaIII, SnIV or BIII, as well as reducing the macrocycles or adding one or two CN- to them. The reaction of GaIIICl(Pc2-) with CN- yields {crypt(K+)}{GaIIICN(Pc˙3-)}˙-·0.5C6H4Cl2 (1) in which the Pc2- macrocycle is reduced to Pc˙3-. Such reduction could probably occur through the addition of CN- to Pc2- forming {GaIII(CN)[Pc(CN)]3-}- which can decompose further interacting with an excess of CN-. As a result, Pc˙3- and cyanogene anions are formed. The interaction of SnIVCl2(TPP2-) with CN- is accompanied by the addition of CN- to the meso-carbon atom of porphyrin forming diamagnetic TPP(CN)3- macrocycles in {crypt(K+)}{SnIV(CN)2[TPP(CN)]3-}- (2). Salt 2 shows a strong NIR absorption band with the maximum at 854 nm whose intensity is comparable with that of the Soret band. The interaction of BIIICl(SubPc2-) with three equivalents of CN- is accompanied by the addition of two CN- to carbon atoms of SubPc2- closest to meso-nitrogen atoms forming {BIII(CN)[SubPc(CN)2]4-}2-. Most probably these dianions transfer electrons to C6H4Cl2 producing the {BIII(CN)[SubPc(CN)2]˙3-}˙- radical anions which form σ-bonded diamagnetic dianions in {crypt(K+)}2{BIII(CN)[SubPc(CN)2]}22-·3C6H4Cl2 (3). The remaining carbon atom closest to the meso-nitrogen atom is involved in this dimerization. According to the calculations, the energy of the C-CN bond is minimal for {GaIII(CN)[Pc(CN)]3-}- enabling further transformation of these anions to {GaIIICN(Pc˙3-)}˙- in 1, whereas cyano-containing anions in 2 and 3 with higher energy of this bond are stable towards the elimination of CN. Optical and magnetic properties of 1-3 together with their crystal and molecular structures are presented. The possible ways of the formation of 1-3 are discussed based on DFT calculations.

Photoactive preorganized subphthalocyanine-based molecular tweezers for selective complexation of fullerenes

The development of new chromophoric receptors capable of binding curved carbon nanostructures is central to the quest for improved fullerene-based organic photovoltaics. We herein report the synthesis and characterization of a subphthalocyanine-based multicomponent ensemble consisting of two electron-rich SubPc-monomers rigidly attached to the convex surface of an electron-poor SubPc-dimer. Such a unique configuration, especially in terms of the two SubPc-monomers, together with the overall stiffness of the linker, endows the multicomponent system with a well-defined tweezer-like topology to efficiently embrace a fullerene in its inner cavity. The formation of a 1 : 1 complex was demonstrated in a variety of titration studies with either C60 or C70. In solution, the underlying association constants were of the order of 105 M-1. Detailed physicochemical experiments revealed a complex scenario of energy- and electron-transfer processes upon photoexcitation in the absence and presence of fullerenes. The close proximity of the fullerenes to the electron-rich SubPcs enables a charge shift from the initially formed reduced SubPc-dimer to either C60 to C70.

Coordination Complexes of Titanium(IV) and Indium(III) Phthalocyanines with Carbonyl-Containing Dyes: The Formation of Singly Bonded Anionic Squarylium Dimers

Reduction methods for the preparation of coordination complexes of titanium(IV) and indium(III) phthalocyanines (Pc) with organic dyes such as indigo, thioindigo, and squarylium dye III (SQ) have been developed, which allow one to obtain crystalline {cryptand(K⁺ )}{(cis-indigo-O,O)^2- Ti^IV (Pc^2- )}(Cl^- )⋅C₆ H₄ Cl₂ (1), {cryptand(K⁺ )}{(cis-thioindigo-O,O)^2- In^III (Pc^2- )}^- ⋅C₆ H₄ Cl₂ (2), and {cryptand(K⁺ )}{[(SQ)₂ -O,O]^2- In^III (Pc^2- )}^- ⋅3.5 C₆ H₄ Cl₂ (3) complexes. The formation of these complexes is accompanied by the reduction of the starting dyes to the anionic state. Transition of trans-indigo or trans-thioindigo to the cis conformation in 1 and 2 provides coordination of both carbonyl oxygen atoms of the dye to Ti^IV Pc or In^III Pc. SQ is reduced to the radical anion state and forms unusual diamagnetic singly bonded (SQ^- )₂ dimers in 3. These dimers have two closely positioned carbonyl oxygen atoms coordinated to In^III Pc. Dianionic Pc^2- macrocycles have been found in 1-3. The complexes contain two chromophore molecules at one metal center. However, their optical spectra are defined mainly by absorption bands of the metal phthalocyanines.

Assessment of electronic transitions involving intermolecular charge transfer in complexes formed by fullerenes and donor–acceptor nanohoops

Inserting an anthraquinone or tetracyanoanthraquinone unit in cycloparaphenylene nanohoops facilitates intermolecular electron transfer to a fullerene guest.

Tetrabutylammonium Salts of Aluminum(III) and Gallium(III) Phthalocyanine Radical Anions Bonded with Fluoren-9-olato- Anions and Indium(III) Phthalocyanine Bromide Radical Anions

Reduction of aluminum(III), gallium(III), and indium(III) phthalocyanine chlorides by sodium fluorenone ketyl in the presence of tetrabutylammonium cations yielded crystalline salts of the type (Bu₄ N⁺ )₂ [M^III (HFl-O^- )(Pc^.3- )]^.- (Br^- )⋅1.5 C₆ H₄ Cl₂ [M=Al (1), Ga (2); HFl-O^- =fluoren-9-olato^- anion; Pc=phthalocyanine] and (Bu₄ N⁺ ) [In^III Br(Pc^.3- )]^.- ⋅0.875 C₆ H₄ Cl₂ ⋅0.125 C₆ H₁₄ (3). The salts were found to contain Pc^.3- radical anions with negatively charged phthalocyanine macrocycles, as evidenced by the presence of intense bands of Pc^.3- in the near-IR region and a noticeable blueshift in both the Q and Soret bands of phthalocyanine. The metal(III) atoms coordinate HFl-O^- anions in 1 and 2 with short Al-O and Ga-O bond lengths of 1.749(2) and 1.836(6) Å, respectively. The C-O bonds [1.402(3) and 1.391(11) Å in 1 and 2, respectively] in the HFl-O^- anions are longer than the same bond in the fluorenone ketyl (1.27-1.31 Å). Salts 1-3 show effective magnetic moments of 1.72, 1.66, and 1.79 μ_B at 300 K, respectively, owing to the presence of unpaired S=1/2 spins on Pc^.3- . These spins are coupled antiferromagnetically with Weiss temperatures of -22, -14, and -30 K for 1-3, respectively. Coupling can occur in the corrugated two-dimensional phthalocyanine layers of 1 and 2 with an exchange interaction of J/k_B =-0.9 and -1.1 K, respectively, and in the π-stacking {[In^III Br(Pc^.3- )]^.- }₂ dimers of 3 with an exchange interaction of J/k_B =-10.8 K. The salts show intense electron paramagnetic resonance (EPR) signals attributed to Pc^.3- . It was found that increasing the size of the central metal atom strongly broadened these EPR signals.

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).

Crystalline salts of metal phthalocyanine radical anions [M(Pc˙3−)]˙− (M = CuII, PbII, VIVO, SnIVCl2) with cryptand(Na+) cations: structure, optical and magnetic properties

Radical anion salts of metal phthalocyanines (M = Cu^II, Pb^II, V^IVO and Sn^IVCl₂) with the {cryptand(Na⁺)} cations have been obtained and studied.

A theoretical study of complexes between fullerenes and concave receptors with interest in photovoltaics

The proper combination of host and guest allows controlling the stability and charge transfer capability of fullerene–concave receptor complexes.

A hindered subphthalocyanine that forms crystals with included aromatic solvent but will not play ball with C60

A novel subphthalocyanine containing bulky substituents placed at its peripheral sites (i.e. 2,3,9,10,16,17-hexa(2′,6′-di-iso-propylphenoxy)boron subphthalocyanine) was prepared and assessed for supramolecular binding with C[Formula: see text], through crystallisation and fluorescence studies. Three different crystal polymorphs of the subphthalocyanine were obtained that showed inclusion of a single aromatic solvent molecule within the well-defined cavity of the molecule but complete exclusion of C[Formula: see text]. Analysis of the crystal structures indicated that the bowl-shaped cavity of the subphthalocyanine molecule was only accessible to small molecules due to the steric congestion surrounding the macrocycle, which results in hindered rotation of the substituents on the NMR timescale. Enhanced solubility, up to 42.0 g/L in common organic solvents, was demonstrated consistent with the crystal structures which are dominated by relatively weak intermolecular interactions, which allow solvent molecules to play a role in crystallisation.