Beyond Binary Co-crystals The Need for Supramolecular Reagents

8 Beyond Binary Co-crystals The Need for Supramolecular Reagents 

4-chlorobenzoic acid Isonicotinamide Isonicotinamide 4-chlorobenzoic acid 

Co-crystal 5, 3-methylbenzoic acid isonicotinamide 3,5-dinitrobenzoic acid (1 1 1), contains the desired three-component supermolecule with the expected connectivity. The stronger acid (pKa=2.8) [145] interacts with the pyridine nitrogen atom, and the weaker acid (pKa=4.3) competes successfully for the amide moiety and forms a heteromeric hydrogen-bonded motif, Fig. 2.5.2. 

Co-crystal 6, 4-(N,N-dimethyl)aminobenzoic acid isonicotinamide 3,5-dinitro-benzoic acid (1 1 1), is also a ternary co-crystal with the intended three-component supermolecule. The acid-pyridine nitrogen interaction persists, and the weaker acid (pKa=6.5) forms a heteromeric motif with the amide moiety, Fig. 2.5.3. 

5-Dinitrobenzoic acid isonicotinamide 4-hydroxy-3-methoxycinnamic acid 7, is also a 1 1 1 ternary co-crystal with the same primary supramolecular connectivity 

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