Andrew S. Paton

Chloro boron subphthalocyanine and its derivatives: dyes, pigments or somewhere in between?

Nine derivatives of chloro boron subphthalocyanine (Cl-BsubPc, 1) have been synthesized and characterized. Seven dimers of Cl-BsubPc have been synthesized by reaction with biphenol (2a), bisphenol A (2b), bisphenol F (2c), bisphenol O (2d), bisphenol P (2e), bisphenol S (2f) and bisphenol Z (2g). For comparison two monomeric phenoxy- (3a) and 4-methylphenoxy (3b) BsubPcs have also been synthesized. Crystals were grown for dimer 2c, whereas all attempts to grow crystals of the remaining dimers resulted in the formation of molecular glasses or amorphous precipitates. Analysis on the structure of 2c suggests that the rigidity and aromatic nature of the central bisphenolic directs the crystal packing. The solubility of the BsubPc dimers in a variety of common organic solvents was measured and compared to that of Cl-BsubPc (2) and monomers 3a and 3b. We have defined ranges for classifying BsubPc derivatives based on their solubility in these solvents: pigment < or = 1 x 10(-8) M, 1 x 10(-3) M < or = pigment-like > 1 x 10(-8) M, 1 x 10(-2) M < or = dye-like > 1 x 10(-3) M, and dye > 1 x 10(-2) M. From this Cl-BsubPc (1) and compounds 2a, 2b, 2c, 2e and 2g are pigment-like while compounds 2d, 2f, 3a and 3b are dye-like. None are exclusively pigments or dyes. In this first approximation of this dye versus pigment classification we have not considered other processes besides solvation which could be undesirable such as polymorphic changes or Ostwald ripening. We have concluded that derivatization of Cl-BsubPc (1) with bisphenols and phenols can be used to control the solubility of BsubPc derivatives. We have also concluded that Cl-BsubPc (1) should not be considered a dye rather is pigment-like in its solubility.

Observations regarding the crystal structures of non-halogenated phenoxyboronsubphthalocyanines having para substituents on the phenoxy group

We report the synthesis and systematic description of a series of five para-substituted phenoxy-BsubPcs including their characterization in the crystal state. The nature of the substituents on the phenoxy molecular fragment was chosen so as to vary both the size and electronegativity: specifically with increasingly bulky para-alkyl groups from hydrogen to tert-octyl and a single electronegative substitute (F). Examination of the arrangement of the phenoxy-BsubPcs within single crystals allows us to place each into one of the two categories. The first, which contains all but one of the derivatives, has a repeating motif which is made up of dimers of the BsubPc molecular fragments. The second, containing only the derivative possessing the large tert-octyl substituent, is characterized by the formation of ribbons instead of dimers of the BsubPc fragment. Regardless of motif the arrangement of the BsubPc molecular fragments was found to be convace–concave.

A role for π–Br interactions in the solid-state molecular packing of para-halo-phenoxy-boronsubphthalocyanines

We report the synthesis and characterization of a series of para-halo-phenoxy-boronsubphthalocyanines (BsubPcs). Across this series, a crystal polymorph of p-bromophenoxy-BsubPc (α-BrPhO-BsubPc) contains a clear and discernible π–Br interaction directing crystallization into a motif not previously seen for phenoxy-BsubPcs.

Pseudohalides of boron subphthalocyanine.

The synthesis and study of a series of pseudohalides of boron subphthalocyanine (BsubPc) are reported. Each pseudohalide has been compared to the more common chloride and bromide of BsubPc, and we have found that most react slower under standard phenoxylation and hydrolysis conditions. Three pseudohalides (TsO-BsubPc, MsO-BsubPc, and BsO-BsubPc) do not hydrolyze at all even after prolonged periods of time in the presence of water. Single crystals of TsO-, MsO-, and ClsO-BsubPc were obtained, and their structures were unambiguously determined.

Modulation of reactive oxygen species photogeneration of bacteriopheophorbide a derivatives by exocyclic E-ring opening and charge modifications.

With the knowledge that the dominant photodynamic therapy (PDT) mechanism of 1a (WST09) switched from type 2 to type 1 for 1b (WST11) upon taurine-driven E-ring opening, we hypothesized that taurine-driven E-ring opening of bacteriochlorophyll derivatives and net-charge variations would modulate reactive oxygen species (ROS) photogeneration. Eight bacteriochlorophyll a derivatives were synthesized with varying charges that either contained the E ring (2a-5a) or were synthesized by taurine-driven E-ring opening (2b-5b). Time-dependent density functional theory (TDDFT) modeling showed that all derivatives would be type 2 PDT-active, and ROS-activated fluorescent probes were used to investigate the photogeneration of a combination of type 1 and type 2 PDT ROS in organic- and aqueous-based solutions. These investigations validated our predictive modeling calculations and showed that taurine-driven E-ring opening and increasing negative charge generally enhanced ROS photogeneration in aqueous solutions. We propose that these structure-activity relationships may provide simple strategies for designing bacteriochlorins that efficiently generate ROS upon photoirradiation.

(Dodecafluorosubphthalocyaninato)(4-methylphenolato)boron(III).

In the title compound, C31H7BF12N6O, molecules are arranged into one-dimensional columns with an intermolecular B⋯B distance of 5.3176 (8) Å. Bowl-shaped molecules are arranged within the columns in a concave bowl-to-ligand arrangement separated by a ring centroid distance of 3.532 (2) Å between the benzene ring of the 4-methylphenoxy ligand and one of the three five-membered rings of a symmetry-related molecule.

Extinction analysis of dielectric multilayer microspheres

This letter reports optical properties of spherical dielectric particles with alternating layers of high and low refractive indices. The authors “predesigned” and synthesized polymer microspheres with alternating polystyrene and poly(trifluoroethyl methacrylate) layers of various thicknesses. Extinction of the microspheres was examined in a broad spectral range. A multipole expansion of electromagnetic field was applied for calculating the extinction efficiency of the particles. Excellent agreement was obtained between experimental and theoretical extinction curves.This letter reports optical properties of spherical dielectric particles with alternating layers of high and low refractive indices. The authors “predesigned” and synthesized polymer microspheres with alternating polystyrene and poly(trifluoroethyl methacrylate) layers of various thicknesses. Extinction of the microspheres was examined in a broad spectral range. A multipole expansion of electromagnetic field was applied for calculating the extinction efficiency of the particles. Excellent agreement was obtained between experimental and theoretical extinction curves.

Sulfonate pseudohalides of boron subphthalocyanine

The crystal structures of three sulfonate pseudohalide derivatives of boron subphthalocyanine (BsubPc) are described and compared with four structures of three published sulfonate derivatives. Benzenesulfonate boron subphthalocyanine [(benzenesulfonato)(subphthalocyaninato)boron, C(30)H(17)BN(6)O(3)S, (I)] crystallizes in the space group P-1 with Z = 2. The structure contains two centrosymmetric π-stacking interactions between the concave faces of the isoindoline units in the BsubPc ligands. 3-Nitrobenzenesulfonate boron subphthalocyanine [(3-nitrobenzenesulfonato)(subphthalocyaninato)boron, C(30)H(16)BN(7)O(5)S, (II)] crystallizes in the space group P2(1)/c with Z = 4. The structure contains an intermolecular S-O···π interaction from the sulfonate group to a five-membered N-containing ring of an isoindoline unit on the concave side of a neighbouring BsubPc ligand, at a distance of 3.151 (3) Å. The crystal of methanesulfonate boron subphthalocyanine [(methanesulfonato)(subphthalocyaninato)boron, C(25)H(15)BN(6)O(3)S, (III)] was produced via sublimation and it is not a solvate, in contrast with two previously published structures of the same compound. Compound (III) crystallizes in the space group P2(1)/n with Z = 2, and its structure is similar to that of the more common compound Cl-BsubPc.

Some observations regarding the behavior of boron subphthalocyanines in polar aprotic solvents

In this paper, we describe some observations from the attempted reaction of Br-BsubPc with phenol in DMF and DMAc. During these efforts, we found that Br-BsubPc reacts with the respective solvents to produce axially substituted formate-BsubPc and acetate-BsubPc. When no phenol is present the reaction proceeds to completion in a relatively short period of time. However, when phenol was present in DMF the reaction produced a mixture of formate-BsubPc, phenoxy-BsubPc, and HO-BsubPc. Similar results were found for the less-reactive Cl-BsubPc and MsO-BsubPc. Aside from these observations, it was found that simple heating in wet acetone of Br-BsubPc quantitatively produced HO-BsubPc after a facile workup. This method of producing HO-BsubPc removes the high temperatures, long reaction times, and harmful chemicals required in other synthetic methods. These results are relevant to anyone considering the reaction of BsubPcs in polar aprotic solvents.

(4-Nitro­phenolato)(subphthalo­cyaninato)boron(III)

The main feature of the structure of the title compound, C30H16BN7O3 or NO2PhO-BsubPc, are pairs of molecules linked through π-interactions between the concave faces of the BsubPc fragments at a distance of 3.5430 (11) Å across an inversion centre. However, the angle between the planes of the five- and six-menbered rings involved in this interaction is 1.44 (10)°, causing the interacting BsubPcs units to be slightly askew rather than parallel as is typical for π-stacking interactions.