Bornane[2,3-b]pyrazino-fused [30]trithiadodecaazahexaphyrin. Synthesis, acid-base behavior and nickel(II) coordination ability

Abstract

Polydentate ligand-bornane[2,3-b]pyrazino-fused [30]trithiadodecaazahexaphyrin has been synthesized by crossover condensation of the racemic mixture of (R/S)-bornane[2[Formula: see text],3[Formula: see text]-b]-2,3-dicyanopyrazine and 2,5-diamino-1,3,4-thiadiazole. Its coordination ability, acid-base behavior and stability were studied by chemical kinetics/thermodynamics, UV-vis spectrophotometry and quantum chemical DFT/B3LYP/6-31G(d,p) methods. The fourth-order kinetic equation with the kinetic constant of 3.38 × 108 s[Formula: see text].mol3.L[Formula: see text] and the association mechanism according to the Langford−Gray classification were established for the fused [30]trithiadodecaazahexaphyrin–nickel diacetate–DMF system. The stepwise protonation of macrocyclic ligand with p[Formula: see text] of -1.41 in CH2Cl2-CF3COOH mixtures at the Hammett acidity functions ([Formula: see text] changed from -2.0 to 2.0 and quantitative parameters of ligand stability in AcOH–H2SO4 mixtures was obtained. The chemical structure of protonated forms and ligand destruction mechanism have been proposed. The obtained results are of interest for development of technological regulations of complex formation and for the transition to the hetero nuclear complexes.