Sustainable Approaches to the Synthesis of Metallophthalocyanines in Solution

This work aims to investigate more sustainable reaction conditions for the synthesis of metallophthalocyanines. Anisole, glycerol and their mixtures have been investigated as reaction media for the tetramerization of phthalonitriles. Acetates of three divalent first-transition metal cations, Co(II), Cu(II) and Zn(II), were used and several bases were tested, depending on the chosen substrates and reaction conditions, with a view to making the whole process more sustainable while ensuring its scalability. Unsubstituted phthalocyanines were synthesized to analyze the behavior of the different metal ions in terms of reactivity in the new reaction media, resulting in a general Cu > Co > Zn trend, while the nonpolar tetra-tert-butyl substitution was investigated to evaluate the synthesis of soluble derivatives in the new conditions. Furthermore, the potassium hydroxide (KOH)-aided statistical synthesis of the unsymmetrical 9(10), 16(17), 23(24)-tri-tert-butyl-2-iodophthalocyaninato zinc(II), starting from 4-tert-butylphthalonitrile and 4-iodophthalonitrile in a glycerol/anisole mixture, proceeded with a satisfactory 26% yield. Our results provide insights into the investigation of new reaction environments and the understanding of their strengths and weaknesses, with a view to further increasing the sustainability of the synthesis of metallomacrocycles with high added value while lowering their production cost.

1,8-Di-aza-bicyclo-[5.4.0]undec-7-en-8-ium bromido-(phthalocyaninato)zincate

The title compound, (C₉H₁₇N₂)[ZnBr(C₃₂H₁₆N₈)], contains a bromido­(phthalocyaninato)zincate anion and a protonated 1,8-di­aza­bicyclo­[5.4.0]undece-7-ene cation, [DBUH]⁺. The central Zn^II atom has a distorted square-pyramidal geometry, with four iso­indole N atoms of the macrocycle in equatorial positions and a bromide ion in the axial position. The latter has a relatively high displacement parameter, but no evidence for disorder was obtained. The central Zn^II atom is displaced by 0.488 (3) Å from the mean plane defined by the four iso­indole N atoms. The [DBUH]⁺ cation is involved in an almost linear N—H⋯Br hydrogen bond. In the crystal, π–π inter­actions lead to a relatively short distance of 3.366 (3) Å between the phthalocyaninate rings.

Zinc phthalocyanine-nicotinamide complexes: evidence of their formation by using spectral studies

Spectral studies and job plot analyses which provide evidence of the formation of complexes of zinc phthalocyanines or zinc naphthalocyanines and nicotinamide or its positional isomers, known as isonicotinamide and picolinamide, are reported. Nicotinamide, isonicotinamide and picolinamide contain the amide group in a different position in the ring and these molecules can coordinate the metal of phthalocyanines through their nitrogen pyridinic atom, or their amide group, to form complexes. FT-IR and NMR spectroscopic studies, as well as job plot analyses in chloroform, have been performed. To validate the formation of complexes, some of them have been isolated, fully characterized and their binding properties and thermal stability have also been investigated.