The crystal structure of the title compound, C5H8N3+·C7H4NO4− or (pydaH)+(pydcH)− (pyda is 2,6‐diamino­pyridine and pydcH2 is pyridine‐2,6‐dicarboxylic acid), shows both intra‐ and inter­molecular proton transfers from carboxyl groups to the ring N atoms of (pydc)2− and pyda. This determination corrects a previous report which formulated this compound as (pydaH2)2+(pydc)2− [Moghimi, Ranjbar, Aghabozorg, Jalali, Shamsipur, Yap & Rahbarnoohi (2002), J. Mol. Struct.605, 133–149]. Ion‐pairing, hydrogen‐bonding and π–π stacking inter­actions link the fragments to form a self‐associated system.

Three new complexes of group thirteen metals, gallium(III), indium(III), and thallium(III) with proton transfer compounds, obtained from 2,6‐pyridinedicarboxylic acid (dipicolinic acid), were synthesized and characterized using elemental analysis, IR, 1H and 13C NMR spectroscopy and single crystal X‐ray diffraction. The gallium(III) and indium(III) complexes were prepared using (pydaH2)(pydc) (pyda = 2,6‐pyridinediamine, pydcH2 = dipicolinic acid) and thallium(III) complex was obtained from (creatH)(pydcH) (creat = creatinine). The chemical formulae and space groups of the complexes are (pydaH)[Ga(pydc)2] · 3.25H2O · CH3OH, $P{\bar 1}$ (1), [In(pydc)(pydcH)(H2O)2] · 5H2O, Pna21 (2) and [Tl2(pydcH)3(pydc)(H2O)2], $P{\bar 1}$ (3). Non‐covalent interactions such as ion‐pairing, hydrogen bonding and π‐π stacking are discussed. The complexation reactions of pyda, pydc, and pyda + pydc with In3+ and Ga3+ ions in aqueous solution were investigated by potentiometric pH titrations, and the equilibrium constants for all major complexes formed are described.

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Copper(II) complex of 4‐(2,2′:6′,2“‐terpyridin‐4′‐yl)toluene(ttpy) was found to be a profitable catalyst for the N‐arylation of a variety of nitrogen‐containing heterocycles, such as some kinds of azoles and a secondary aliphatic amine, with aryl halides (iodides, bromides, and chlorides) under moderate conditions. A variety of functionalized aryl halides were tolerated in good to excellent yields by this air stable and low cost Cu(II)‐based catalytic system. Phenyl boronic acid was also used as an alternative to aryl halides to supply aryl moiety.