The synthesis and characterization of nonperipherally tetra terminal alkynyl substituted phthalocyanines and glycoconjugation via the click reaction

In order to obtain nonperipherally tetra terminal alkynyl substituted phthalocyanines (Pcs), new 3-pent-4-ynyloxy phthalonitrile (3) was prepared by the nucleophilic displacement reaction of 3-nitrophthalonitrile (1) and 4-pentyn-1-ol (2) and then cyclotetramerization was attained in the presence of zinc acetate, cobalt acetate, and/or DBU in n-pentanol without protection/deprotection. For the first time, the glycoconjugation of the nonperipherally tetra terminal alkynyl substituted zinc phthalocyanine (ZnPc) (6) can be easily achieved via the click reaction in a high yield. The electronic absorption spectrum of the glucopyranosyl substituted ZnPc (10) derivative showed a red-shifted Q band at 751 nm in dichloromethane due to the protonation of the meso nitrogens of the Pc macrocycle. Deacylation yielded ZnPc (11) bearing glucose substituents at nonperipheral positions with an improved water-solubility and non-aggregation in DMSO. The chemical structures of the new compounds were characterized by (1)H NMR, (13)C NMR, FT-IR, UV-Vis, mass spectrometry and elemental analysis. Moreover, the phthalonitrile compound was characterized using X-ray.

Routes to some 3,6-disubstituted phthalonitriles and examples of phthalocyanines derived therefrom: An overview

The paper reviews a selection of synthetic pathways that provide access to 3,6-disubstituted phthalonitriles, precursors for the synthesis of 1,4,8,11,15,18,22,25-octasubstituted phthalocyanine derivatives. Early routes using Diels–Alder reactions for the synthesis of 3,6-dialkyl, 3,6-dialkoxymethyl, 3,6-dialkenyl and 3,6-diphenylphthalonitriles are appraised. However, the emphasis of the review focuses on the scope and applications of 2,3-dicyanohydroquinone as a starting material for obtaining 3,6-disubstituted phthalonitriles. The earliest example of the use of 2,3-dicyanohydroquinone concerned its O -alkylation to afford 3,6-dialkoxyphthalonitriles. These are immediate precursors to near-infrared absorbing phthalocyanine derivatives. Triflation of 2,3-dicyanohydroquinone extends the scope of the compound for phthalocyanine synthesis; the bis-triflate derivative is susceptible to S N Ar reactions and readily reacts with thiols to provide 3,6-bis(alkylsulfanyl) and 3,6-bis(arylsulfanyl)phthalonitriles. 3,6-Bis(phenylselenyl)phthalonitrile has also been obtained recently from the same precursor. Phthalocyanine derivatives obtained from them typically show a strongly bathochromically shifted Q-band absorption that is particularly sensitive to the central metal ion. The bis-triflate of 2,3-dicyanohydroquinone is also an ideal precursor for participation in cross-coupling reactions. Examples from the University of East Anglia group and elsewhere are presented which show the application of the nickel-catalyzed Negishi coupling reaction using alkylzinc halide derivatives. Yields of 3,6-dialkylphthalonitriles and 3,6-bis(substituted alkyl)phthalonitriles range from ca. 40 to 70%. Direct comparison for one example shows that the yield from the Negishi coupling method is higher than that using the Suzuki coupling protocol. Examples of the preparation of 3,6-diarylphthalonitriles from 2,3-dicyanohydroquinone bis-triflate using the Suzuki coupling reaction are reported with yields of the order of 65–70%. The review also includes a further application of 2,3-dicyanohydroquinone as a precursor to both monobromo and dibromo derivatives of 3,6-dibutoxyphthalonitrile. These compounds provide opportunities for cross-coupling at the brominated sites to provide more complex derivatives with the potential to serve as precursors of highly substituted phthalocyanine derivatives.

Synthesis and characterization of some octaalkyl substituted lead phthalocyanines and unexpected variations in lead lability arising from the position of substituents and their chain length

The preparation of some peripherally substituted (2,3,9,10,16,17,23,24) and non-peripherally substituted (1,4,8,11,15,18,22,25) octaalkyl lead(II) phthalocyanines with different alkyl chain lengths (6, 7, 8 or 9 carbons) is described and a comparison of some of their properties reported. X-ray structure analyses of the isomeric peripheral and non-peripheral octakis(octyl)phthalocyaninato lead(II) compounds reveal a greater degree of distortion of the ligand ring system from planarity in the former derivative. The series of peripherally substituted octaalkyl lead(II) phthalocyanines exhibit columnar liquid crystal behavior whereas the non-peripherally substituted isomers do not. The lability of the lead ion was investigated using 1 H NMR spectrometry under a specific set of conditions (8.8 × 10-4 M solutions of the phthalocyanine in d8-toluene containing d4-acetic acid 2.06 × 10-5 M). All the compounds underwent acid catalyzed demetalation at rates dependent upon the location of the substituents and, more surprisingly, the chain length of the alkyl groups. Under these conditions the lead ion within each of the peripherally substituted octaalkyl lead phthalocyanines was more labile than that in the non-peripherally substituted isomer.

2,2,3,3-Tetrafluoropropoxy substituted oxo-titanium phthalocyanines axially ligated with common MALDI matrix materials

The synthesis of tetra and octa 2,2,3,3-tetrafluoropropoxy substituted oxo-titanium phthalocyanines (TiOPc) are reported. Using strongly chelating oxygen donor ligands, the reactions of TiOPc with catecholate (1a, 2a), 4-nitrocatecholate (1b, 2b) and caffeic acid (1c, 2c), ellagic acid (1d, 2d) and chlorogenic acid (1e, 2e) are described. The new compounds were characterized by mass, 1 H NMR, FT-IR, and UV-vis spectroscopic techniques as well as elemental analysis.

Aggregation equilibria of amphiphilic phthalocyanines substituted by polyethylene oxide in dichloromethane

The aggregation equilibria of metal-free and copper(II) phthalocyanine compounds substituted by polyethylene oxide at β (2 or 3, 9 or 10, 16 or 17, 23 or 24) positions, TDEO6-MPc, in deuterated dichloromethane were studied by means of 1H NMR spectroscopy. Where the side chain polyethylene oxide is hexaethyleneglycolmonododecylether (DEO6). The results of concentration dependence of 1H NMR signals reveal that the metal-free phthalocyanine TDEO6-H2Pc and copper complex TDEO6-CuPc successively form the aggregates up to trimer and tetramer in the concentration range of Pc, C Pc = 10-5.5–10-1.5 M , respectively. Formation constants and chemical shifts of each aggregate were determined by non-linear regression analysis of chemical shift change. The structures of TDEO6-MPc aggregates were estimated as TDEO6-MPc is successively stacked face to face. The phthalocyanine rings in the aggregate is slipped between them, the slippage, however, is not so large. DEO6 side chains are flexible and move freely.

Solvent effect on the aggregation of amphiphilic phthalocyanines substituted by polyethyleneoxide

Metal-free and copper(II) tetra-β-polyethyleneoxide-substituted phthalocyanine derivatives, TDEO6-MPc, where polyethylene oxide derivative is hexaethyleneglycolmonododecylether (DEO6), were synthesized. Those compounds are soluble in both lipophilic and hydrophilic solvents. By taking advantage of this amphiphilic property, solvent effect on the aggregation of the phthalocyanine was studied by means of UV-vis absorption and fluorescence spectroscopies. Dimerization constants of TDEO6-MPc in non-coordinating solvents were determined by the concentration dependence of absorption spectra. Aggregation is suppressed by the increase in the E T (30) value (acceptor property) of solvents in non-coordinating solvents, whereas it is promoted by the increase in Donor Number (donor property) of solvent in coordinating solvents.