Neutral, Zwitterion, Ionic Forms of 5‐Aminoisophthalic Acid in Cocrystals, Salts and Their Optical Properties

Abstract

Different ionic and zwitterionic forms of amphoteric 5‐aminoisophthalic acid were observed in the self‐assemblies of five salts and in a cocrystal. The presence of these forms of the molecule caused differences in respective local environments, which were reflected in corresponding absorption and emission spectra in solid state. Dianion of the acid was observed in hydrated 1:2 salt with 6‐methylpyridin‐2‐amine whereas the salt of 5‐methylthiazol‐2‐amine had the zwitterionic anion. The mono‐anion of the 5‐aminoisophthalic acid was observed in the salt of 4,6‐dimethylpyrimidin‐2‐amine. The self‐assembly of the 1:1 cocrystal of caffeine with 5‐aminoisophthalic acid had neutral form of the acid and the cationic form of the acid was observed in the perchlorate and bromide salts. DFT‐calculation with using CAMB3LYP functional with 6–31+G (d,p) as basis set in gas‐phase showed that different HOMO‐LUMO gaps of the neutral, cation and anion forms and these were reflected in the corresponding UV‐visible spectra of the salt. The changes in intra‐molecular charge transfer (ICT) fluorescence emissions in solid samples due to the different ionic forms were demonstrated.

Sensing Capacity in Dysprosium Metal–Organic Frameworks Based on 5-Aminoisophthalic Acid Ligand

“…The luminescence properties of compounds 1 and 2 were first studied in the solid state by measuring the excitation and emission spectra at room temperature over the polycrystalline samples. The emission spectrum of compound 1, measured under monochromated laser irradiation (λ ex = 325 nm), is dominated by a wide band covering the 400-500 nm range (Figure 3), which may be attributed to the ligand fluorescence, in view of the similar profile shown by the free ligand, as described in a previous study [19]. In particular, the band may be assigned to the π ← π* transitions occurring at the aromatic ring of the ligand, as previously shown for other compounds based on the 5aip ligand [20,21].…”

New Cocrystallization Method: Non-photochemical Laser-Induced Nucleation of a Cocrystal of Caffeine–Gallic Acid in Water

“…More than 30 cocrystals have been reported between CAF and carboxylic acids. Among them, one can mention oxalic acid, malonic acid, maleic acid, glutaric acid, formic acid, acetic acid, trifluoroacetic acid, citric acid, succinic acid, 2-, 3-, 4-hydroxybenzoic- and 2,3-, 2,4-, 2,5-, 3,4-, and 3,5-dihydroxybenzoic acid, gallic acid, − 2-hydroxy-1-naphthoic acid, p -coumaric acid, 4-hydroxybenzoic acid, benzoic acid, p -formylphenoxyacetic acid, 1- and 2-naphthoxyacetic acid, dipicolinic acid, 4-chloro-3-nitrobenzoic acid, cinnamic acid, mesaconic acid, dimethylsuccinic acid, L-malic acid, anthranilic acid, 5-aminoisophthalic acid, 3-nitrobenzoic acid, tannic acid, glycolic acid, trimesic acid, isophthalic acid, benzene-1,3,5-tricarboxylic, and benzene-1,2,3-tricarboxylic acid . In some cases, CAF is used in a drug–drug cocrystal such as with saccharin, quercetin, eosin, theophylline, sulfacetamide, furosemide, genistein, myricetin, dihydromyricetin, 4-aminosalicylic acid, baicalein, epalrestat, indomethacin, paracetamol, zonisamide, dapsone, 5-fluorocytosine, luteolin, naringenin, fisetin, famotidine, hydrochlorothiazide, apixaban, pyrimethamine, niflumic acid, and chlorthalidone …”

Arrangements of fluorophores in the salts of imidazole tethered anthracene derivatives with pyridinedicarboxylic acids influencing photoluminescence

“…17 However, the photoluminescence properties of assemblies having arrays of symmetry non-equivalent molecules 16 have not been dealt with. Besides these, the photoluminescence of cocrystals is influenced by the local environment, 18,19 which also helps in ion recognitions. 8 As a matter of fact, 2,6-pyridinedicarboxylic acid has the ability to modulate the photoluminescence of nanomaterials.…”

“…This suggest that the exception can be made over the type of salts of Hanthraimida with organic carboxylic acids where in general the mono-cationic slats dominated. [17][18] There are limited examples of assemblies containing conjugate acid or base part as neutral components in organic salts [37][38][39] and inorganic complexes. 40 Any of the three forms of the pyridinedicarboxylic acids, namely, the neutral, mono-carboxylate From such a small difference of pKa, one would expect similar cocrystal from the two positional isomers of H 2 pdc, [11][12] but it did not happen.…”