Ashwini Nangia - Academia.edu (original) (raw)

Papers by Ashwini Nangia

Crystal Growth & Design, 2005

... b) Datta, S.; Grant, DJW Nature Rev.2004, 3, 42. ... Ensembles: Acid−Pyridine and Acid−Carbon... more ... b) Datta, S.; Grant, DJW Nature Rev.2004, 3, 42. ... Ensembles: Acid−Pyridine and Acid−Carbonyl Synthons for Multicomponent Materials. Ramkinkar Santra and Kumar Biradha. Crystal Growth & Design 2009 9 (11), 4969-4978. ...

Crystengcomm, 2005

... From binary to ternary cocrystals. Balakrishna R. Bhogala, Srinivas Basavoju and Ashwini Nang... more ... From binary to ternary cocrystals. Balakrishna R. Bhogala, Srinivas Basavoju and Ashwini Nangia*. School of Chemistry, University of Hyderabad, Hyderabad 500 046, India. E-mail: ashwini_nangia@rediffmail.com; Fax: +91 40 23011338; Tel: +91 40 23011338. ...

Crystal Growth & Design, 2004

Cocrystallization is a current theme in several research groups to study hydrogen bonding by X-ra... more Cocrystallization is a current theme in several research groups to study hydrogen bonding by X-ray diffraction, for the synthesis of supramolecular architectures and interpenetrated networks, and in pharmaceutical development. 6 Carboxylic acids and carboxamides are ...

Crystal Growth & Design, 2003

Crystallization of R,ω-alkanedicarboxylic acids (HOOC-(CH 2 ) n-2 -COOH, n ) 2-6) with isonicotin... more Crystallization of R,ω-alkanedicarboxylic acids (HOOC-(CH 2 ) n-2 -COOH, n ) 2-6) with isonicotinamide (IN) is carried out in 1:2 and 1:1 stoichiometry. Five cocrystals of (diacid)‚(IN) 2 composition (diacid ) oxalic acid, malonic acid, succinic acid, glutaric acid, and adipic acid) are characterized by X-ray diffraction at 153(2) K. Tapes of acid-pyridine O-H‚‚‚N and amide-amide N-H‚‚‚O hydrogen bond synthons stabilize these five crystal structures as predicted by the hierarchic model: the best donor (COOH) and best acceptor group (pyridine N) hydrogen bond as acid-pyridine and the second best donor-acceptor group (CONH 2 ) aggregates as an amide dimer. Glutaric acid and adipic acid cocrystallize in 1:1 stoichiometry also, (diacid)‚(IN), with acid-pyridine and acid-amide hydrogen bonds. Synthon energy calculations (∆E synthon , RHF/6-31G**) explain the observed hydrogen bond preferences in 1:2 (five examples) and 1:1 (two examples) cocrystals. The acid-pyridine hydrogen bond is favored over the acidamide dimer for strong carboxylic acids because the difference between ∆E acid-pyridine and ∆E acid-amide (-2.21 kcal mol -1 ) is greater than the difference for weak acids (-0.77 kcal mol -1 ), which cocrystallize with both of these hydrogen bond synthons. We suggest ∆E synthon as a semiquantitative parameter to rank hydrogen bond preferences and better understand supramolecular organization in the multifunctional acid-IN system. Melting point alternation in five homologous (diacid)‚(IN) 2 cocrystals is correlated with changes in crystal density and packing fraction.

Chemical Communications, 2002

Analysis of phenyl-perfluorophenyl stacking synthon, C-H...F, C-F...pi interactions, and F...F te... more Analysis of phenyl-perfluorophenyl stacking synthon, C-H...F, C-F...pi interactions, and F...F tetramer in three closely related azine crystal structures shows the dominance of Ar-ArF synthon while other interactions are turned on/off depending on the H/F stoichiometry in the molecule.

Chemical Communications, 2006

The novel carboxamide-pyridine N-oxide synthon, sustained via N-H...O- hydrogen bonding and C-H..... more The novel carboxamide-pyridine N-oxide synthon, sustained via N-H...O- hydrogen bonding and C-H...O interaction, is shown to assemble isonicotinamide N-oxide in a triple helix architecture and the same heterosynthon is exploited to synthesize cocrystals of barbiturate drugs with 4,4'-bipyridine N,N'-dioxide.

Crystal Growth & Design, 2006

Crystal structures of mono-and diaryl ureas are well-known in the crystal engineering literature.... more Crystal structures of mono-and diaryl ureas are well-known in the crystal engineering literature. 1 The dominant recognition motif in N,N'-diaryl ureas is the α-network, a chain of bifurcated N−H···O hydrogen bonds between NH donors and the C O acceptor (Scheme 1). The ...

Chemistry-a European Journal, 2005

The T-shaped host molecule 4,4-bis(4′-hydroxyphenyl)cyclohexanone (1) has an equatorial phenol gr... more The T-shaped host molecule 4,4-bis(4′-hydroxyphenyl)cyclohexanone (1) has an equatorial phenol group and a cyclohexanone group along the arms and an axial phenol ring as the stem. The equatorial phenyl ring adopts a “shut” or “open” conformation, like a windowpane, depending on the size of the guest (phenol or o/m-cresol), for the rectangular voids of the hydrogen-bonded ladder host framework. The adaptable cavity of host 1 expands to 11×15–18 Å through the inclusion of water with the larger cresol and halophenol guests (o-cresol, m-cresol, o-chlorophenol, and m-bromophenol) compared with a size of 10×13 Å for phenol and aniline inclusion. The ladder host framework of 1 is chiral (P21) with phenol, whereas the inclusion of isosteric o- and m-fluorophenol results in a novel polar brick-wall assembly (7×11 Å voids) as a result of auxiliary CH⋅⋅⋅F interactions. The conformational flexibility of strong OH⋅⋅⋅O hydrogen-bonding groups (host 1, phenol guest), the role of guest size (phenol versus cresol), and weak but specific intermolecular interactions (herringbone T-motif, CH⋅⋅⋅F interactions) drive the crystallization of T-host 1 towards 1D ladder and 2D brick-wall structures, that is, supramolecular isomerism. Host 1 exhibits selectivity for the inclusion of aniline in preference to phenol as confirmed by X-ray diffraction, 1H NMR spectroscopy, and thermogravimetry-infrared (TG-IR) analysis. The Tonset value (140 °C) of aniline in the TGA is higher than those of phenol and the higher-boiling cresol guests (Tonset=90–110 °C) because the former structure has more OH⋅⋅⋅N/NH⋅⋅⋅O hydrogen bonds than the clathrate of 1 with phenol which has OH⋅⋅⋅O hydrogen bonds. Guest-binding selectivity for same-sized phenol/aniline molecules as a result of differences in hydrogen-bonding motifs is a notable property of host 1. Host–guest clathrates of 1 provide an example of spontaneous chirality evolution during crystallization and a two-in-one host–guest crystal (phenol and aniline), and show how weak CH⋅⋅⋅F interactions (o- and m-fluorophenol) can change the molecular arrangement in strongly hydrogen-bonded crystal structures.

Chemical Communications, 2005

Water helices surrounding the nano-channels of trichlorophloroglucinol and tribromophloroglucinol... more Water helices surrounding the nano-channels of trichlorophloroglucinol and tribromophloroglucinol have different handedness, PMPMPM and PPPMMM (P = right-handed, M = left-handed), depending on halogenhalogen interactions between the host molecules.

Crystal Growth & Design, 2005

The hexagonal layer structure of host atoms in chloro, bromo, and iodo derivatives of 2,4,6-tris ... more The hexagonal layer structure of host atoms in chloro, bromo, and iodo derivatives of 2,4,6-tris (4-halophenoxy)-1,3,5-triazine, X-POT, is stabilized by a cyclic and cooperative halogen trimer (X···X) synthon. The X···X distance is 3.5 Å in isostructural channel inclusion adducts of Cl-...

Crystal Growth & Design, 2006

Halogen atoms Cl, Br, and I steer crystallization of 2-halo-3-hydroxypyridine 1, pyridine-N-oxide... more Halogen atoms Cl, Br, and I steer crystallization of 2-halo-3-hydroxypyridine 1, pyridine-N-oxides 2, and 2-halo-3aminopyridine 3 in noncentrosymmetric space groups efficient for nonlinear optical materials. Whereas the strong hydrogen-bond chains are aligned antiparallel, the L-or V-geometry of weak interhalogen interaction steers polar alignment in the solid state, even for high dipole moment (µ) halogenated N-oxides 2 (µ > 5.0 D). Six out of seven structures evaluated crystallize in polar/chiral space groups due to interhalogen interactions compared to the one in six probability of noncentrosymmetric packing for achiral molecules.

Chemical Communications, 2006

A T6(2) tape of hydrogen bonded water molecules in boat cyclohexane conformation resides in the c... more A T6(2) tape of hydrogen bonded water molecules in boat cyclohexane conformation resides in the channel structure of a dibromophloroglucinol (DBPG) host; water escapes at 40-90 degrees C but is readily re-absorbed by the sponge-like apohost.

Crystengcomm, 2005

... Binoy K. Sahaa, Ashwini Nangia*a and Mariusz Jaskólski*b. a School of Chemistry, University o... more ... Binoy K. Sahaa, Ashwini Nangia*a and Mariusz Jaskólski*b. a School of Chemistry, University of Hyderabad, Hyderabad 500 046, India. ... bonding,9 which includes the interaction of soft donor halogens (I, Br) with electronegative heteroatoms (O, N). It is a Lewis acid–Lewis base ...

Crystal Growth & Design, 2003

... Balakrishna R. Bhogala and Ashwini Nangia*. School of Chemistry, University of Hyderabad, Hyd... more ... Balakrishna R. Bhogala and Ashwini Nangia*. School of Chemistry, University of Hyderabad, Hyderabad 500 046, India. Crystal Growth & Design , 2003, 3 (4), pp 547–554. DOI: 10.1021/cg034047i. Publication Date (Web): June ...

Crystal Growth & Design, 2002

Journal of The American Chemical Society, 1998

The principles of crystal engineering have been used to design a family of structures with potent... more The principles of crystal engineering have been used to design a family of structures with potential as octupolar nonlinear optical (NLO) materials. The major aim in such an exercise, a carry-over of molecular symmetry into the crystal, is possible with a retrosynthetic approach. An ...

Acta Crystallographica Section A, 1998

The one is the (o %o4#, or the principle of synthesis, and has for its objects those forms which ... more The one is the (o %o4#, or the principle of synthesis, and has for its objects those forms which are common to universal nature and existence itself; the other is the (o !o4# or principle of analysis, and its action regards the relations of things, simply as relations; F F F . Reason respects the differences, and imagination the similitudes of things. Reason is to the imagination as the instrument to the agent, as the body to the spirit, as the shadow to the substance.

Crystengcomm, 2003

CrystEngComm, 2003, 5, 164-168 DOI:10.1039/B304078J (Paper). Supramolecular synthons in phenol–is... more CrystEngComm, 2003, 5, 164-168 DOI:10.1039/B304078J (Paper). Supramolecular synthons in phenol–isonicotinamide adducts. Peddy Vishweshwara, Ashwini Nangia*a and Vincent M. Lynchb. a School of Chemistry, University of Hyderabad, Hyderabad, 500 046, India. ...

Journal of Organic Chemistry, 2002

X-ray crystal structures of pyrazinic acid 1 and isomeric methylpyrazine carboxylic acids 2-4 are... more X-ray crystal structures of pyrazinic acid 1 and isomeric methylpyrazine carboxylic acids 2-4 are analyzed to examine the occurrence of carboxylic acid-pyridine supramolecular synthon V in these heterocyclic acids. Synthon V, assembled by (carboxyl)O-H...N(pyridine) and (pyridine)C-H...O(carbonyl) hydrogen bonds, controls self-assembly in the crystal structures of pyridine and pyrazine monocarboxylic acids. The recurrence of acid-pyridine heterodimer V compared to the more common acid-acid homodimer I in the crystal structures of pyridine and pyrazine monocarboxylic acids is explained by energy computations in the RHF 6-31G* basis set. Both the O-H.N and the C-H...O hydrogen bonds in synthon V result from activated acidic donor and basic acceptor atoms in 1-4. Pyrazine 2,3- and 2,5-dicarboxylic acids 10 and 11 crystallize as dihydrates with a (carboxyl)O-H...O(water) hydrogen bond in synthon VII, a recurring pattern in the diacid structures. In summary, the carboxylic acid group forms an O-H...N hydrogen bond in pyrazine monocarboxylic acids and an O-H...O hydrogen bond in pyrazine dicarboxylic acids. This structural analysis correlates molecular features with supramolecular synthons in pyridine and pyrazine carboxylic acids for future crystal engineering strategies.

Crystal Growth & Design, 2005

... b) Datta, S.; Grant, DJW Nature Rev.2004, 3, 42. ... Ensembles: Acid−Pyridine and Acid−Carbon... more ... b) Datta, S.; Grant, DJW Nature Rev.2004, 3, 42. ... Ensembles: Acid−Pyridine and Acid−Carbonyl Synthons for Multicomponent Materials. Ramkinkar Santra and Kumar Biradha. Crystal Growth & Design 2009 9 (11), 4969-4978. ...

Crystengcomm, 2005

... From binary to ternary cocrystals. Balakrishna R. Bhogala, Srinivas Basavoju and Ashwini Nang... more ... From binary to ternary cocrystals. Balakrishna R. Bhogala, Srinivas Basavoju and Ashwini Nangia*. School of Chemistry, University of Hyderabad, Hyderabad 500 046, India. E-mail: ashwini_nangia@rediffmail.com; Fax: +91 40 23011338; Tel: +91 40 23011338. ...

Crystal Growth & Design, 2004

Cocrystallization is a current theme in several research groups to study hydrogen bonding by X-ra... more Cocrystallization is a current theme in several research groups to study hydrogen bonding by X-ray diffraction, for the synthesis of supramolecular architectures and interpenetrated networks, and in pharmaceutical development. 6 Carboxylic acids and carboxamides are ...

Crystal Growth & Design, 2003

Crystallization of R,ω-alkanedicarboxylic acids (HOOC-(CH 2 ) n-2 -COOH, n ) 2-6) with isonicotin... more Crystallization of R,ω-alkanedicarboxylic acids (HOOC-(CH 2 ) n-2 -COOH, n ) 2-6) with isonicotinamide (IN) is carried out in 1:2 and 1:1 stoichiometry. Five cocrystals of (diacid)‚(IN) 2 composition (diacid ) oxalic acid, malonic acid, succinic acid, glutaric acid, and adipic acid) are characterized by X-ray diffraction at 153(2) K. Tapes of acid-pyridine O-H‚‚‚N and amide-amide N-H‚‚‚O hydrogen bond synthons stabilize these five crystal structures as predicted by the hierarchic model: the best donor (COOH) and best acceptor group (pyridine N) hydrogen bond as acid-pyridine and the second best donor-acceptor group (CONH 2 ) aggregates as an amide dimer. Glutaric acid and adipic acid cocrystallize in 1:1 stoichiometry also, (diacid)‚(IN), with acid-pyridine and acid-amide hydrogen bonds. Synthon energy calculations (∆E synthon , RHF/6-31G**) explain the observed hydrogen bond preferences in 1:2 (five examples) and 1:1 (two examples) cocrystals. The acid-pyridine hydrogen bond is favored over the acidamide dimer for strong carboxylic acids because the difference between ∆E acid-pyridine and ∆E acid-amide (-2.21 kcal mol -1 ) is greater than the difference for weak acids (-0.77 kcal mol -1 ), which cocrystallize with both of these hydrogen bond synthons. We suggest ∆E synthon as a semiquantitative parameter to rank hydrogen bond preferences and better understand supramolecular organization in the multifunctional acid-IN system. Melting point alternation in five homologous (diacid)‚(IN) 2 cocrystals is correlated with changes in crystal density and packing fraction.

Chemical Communications, 2002

Analysis of phenyl-perfluorophenyl stacking synthon, C-H...F, C-F...pi interactions, and F...F te... more Analysis of phenyl-perfluorophenyl stacking synthon, C-H...F, C-F...pi interactions, and F...F tetramer in three closely related azine crystal structures shows the dominance of Ar-ArF synthon while other interactions are turned on/off depending on the H/F stoichiometry in the molecule.

Chemical Communications, 2006

The novel carboxamide-pyridine N-oxide synthon, sustained via N-H...O- hydrogen bonding and C-H..... more The novel carboxamide-pyridine N-oxide synthon, sustained via N-H...O- hydrogen bonding and C-H...O interaction, is shown to assemble isonicotinamide N-oxide in a triple helix architecture and the same heterosynthon is exploited to synthesize cocrystals of barbiturate drugs with 4,4'-bipyridine N,N'-dioxide.

Crystal Growth & Design, 2006

Crystal structures of mono-and diaryl ureas are well-known in the crystal engineering literature.... more Crystal structures of mono-and diaryl ureas are well-known in the crystal engineering literature. 1 The dominant recognition motif in N,N'-diaryl ureas is the α-network, a chain of bifurcated N−H···O hydrogen bonds between NH donors and the C O acceptor (Scheme 1). The ...

Chemistry-a European Journal, 2005

The T-shaped host molecule 4,4-bis(4′-hydroxyphenyl)cyclohexanone (1) has an equatorial phenol gr... more The T-shaped host molecule 4,4-bis(4′-hydroxyphenyl)cyclohexanone (1) has an equatorial phenol group and a cyclohexanone group along the arms and an axial phenol ring as the stem. The equatorial phenyl ring adopts a “shut” or “open” conformation, like a windowpane, depending on the size of the guest (phenol or o/m-cresol), for the rectangular voids of the hydrogen-bonded ladder host framework. The adaptable cavity of host 1 expands to 11×15–18 Å through the inclusion of water with the larger cresol and halophenol guests (o-cresol, m-cresol, o-chlorophenol, and m-bromophenol) compared with a size of 10×13 Å for phenol and aniline inclusion. The ladder host framework of 1 is chiral (P21) with phenol, whereas the inclusion of isosteric o- and m-fluorophenol results in a novel polar brick-wall assembly (7×11 Å voids) as a result of auxiliary CH⋅⋅⋅F interactions. The conformational flexibility of strong OH⋅⋅⋅O hydrogen-bonding groups (host 1, phenol guest), the role of guest size (phenol versus cresol), and weak but specific intermolecular interactions (herringbone T-motif, CH⋅⋅⋅F interactions) drive the crystallization of T-host 1 towards 1D ladder and 2D brick-wall structures, that is, supramolecular isomerism. Host 1 exhibits selectivity for the inclusion of aniline in preference to phenol as confirmed by X-ray diffraction, 1H NMR spectroscopy, and thermogravimetry-infrared (TG-IR) analysis. The Tonset value (140 °C) of aniline in the TGA is higher than those of phenol and the higher-boiling cresol guests (Tonset=90–110 °C) because the former structure has more OH⋅⋅⋅N/NH⋅⋅⋅O hydrogen bonds than the clathrate of 1 with phenol which has OH⋅⋅⋅O hydrogen bonds. Guest-binding selectivity for same-sized phenol/aniline molecules as a result of differences in hydrogen-bonding motifs is a notable property of host 1. Host–guest clathrates of 1 provide an example of spontaneous chirality evolution during crystallization and a two-in-one host–guest crystal (phenol and aniline), and show how weak CH⋅⋅⋅F interactions (o- and m-fluorophenol) can change the molecular arrangement in strongly hydrogen-bonded crystal structures.

Chemical Communications, 2005

Water helices surrounding the nano-channels of trichlorophloroglucinol and tribromophloroglucinol... more Water helices surrounding the nano-channels of trichlorophloroglucinol and tribromophloroglucinol have different handedness, PMPMPM and PPPMMM (P = right-handed, M = left-handed), depending on halogenhalogen interactions between the host molecules.

Crystal Growth & Design, 2005

The hexagonal layer structure of host atoms in chloro, bromo, and iodo derivatives of 2,4,6-tris ... more The hexagonal layer structure of host atoms in chloro, bromo, and iodo derivatives of 2,4,6-tris (4-halophenoxy)-1,3,5-triazine, X-POT, is stabilized by a cyclic and cooperative halogen trimer (X···X) synthon. The X···X distance is 3.5 Å in isostructural channel inclusion adducts of Cl-...

Crystal Growth & Design, 2006

Halogen atoms Cl, Br, and I steer crystallization of 2-halo-3-hydroxypyridine 1, pyridine-N-oxide... more Halogen atoms Cl, Br, and I steer crystallization of 2-halo-3-hydroxypyridine 1, pyridine-N-oxides 2, and 2-halo-3aminopyridine 3 in noncentrosymmetric space groups efficient for nonlinear optical materials. Whereas the strong hydrogen-bond chains are aligned antiparallel, the L-or V-geometry of weak interhalogen interaction steers polar alignment in the solid state, even for high dipole moment (µ) halogenated N-oxides 2 (µ > 5.0 D). Six out of seven structures evaluated crystallize in polar/chiral space groups due to interhalogen interactions compared to the one in six probability of noncentrosymmetric packing for achiral molecules.

Chemical Communications, 2006

A T6(2) tape of hydrogen bonded water molecules in boat cyclohexane conformation resides in the c... more A T6(2) tape of hydrogen bonded water molecules in boat cyclohexane conformation resides in the channel structure of a dibromophloroglucinol (DBPG) host; water escapes at 40-90 degrees C but is readily re-absorbed by the sponge-like apohost.

Crystengcomm, 2005

... Binoy K. Sahaa, Ashwini Nangia*a and Mariusz Jaskólski*b. a School of Chemistry, University o... more ... Binoy K. Sahaa, Ashwini Nangia*a and Mariusz Jaskólski*b. a School of Chemistry, University of Hyderabad, Hyderabad 500 046, India. ... bonding,9 which includes the interaction of soft donor halogens (I, Br) with electronegative heteroatoms (O, N). It is a Lewis acid–Lewis base ...

Crystal Growth & Design, 2003

... Balakrishna R. Bhogala and Ashwini Nangia*. School of Chemistry, University of Hyderabad, Hyd... more ... Balakrishna R. Bhogala and Ashwini Nangia*. School of Chemistry, University of Hyderabad, Hyderabad 500 046, India. Crystal Growth & Design , 2003, 3 (4), pp 547–554. DOI: 10.1021/cg034047i. Publication Date (Web): June ...

Crystal Growth & Design, 2002

Journal of The American Chemical Society, 1998

The principles of crystal engineering have been used to design a family of structures with potent... more The principles of crystal engineering have been used to design a family of structures with potential as octupolar nonlinear optical (NLO) materials. The major aim in such an exercise, a carry-over of molecular symmetry into the crystal, is possible with a retrosynthetic approach. An ...

Acta Crystallographica Section A, 1998

The one is the (o %o4#, or the principle of synthesis, and has for its objects those forms which ... more The one is the (o %o4#, or the principle of synthesis, and has for its objects those forms which are common to universal nature and existence itself; the other is the (o !o4# or principle of analysis, and its action regards the relations of things, simply as relations; F F F . Reason respects the differences, and imagination the similitudes of things. Reason is to the imagination as the instrument to the agent, as the body to the spirit, as the shadow to the substance.

Crystengcomm, 2003

CrystEngComm, 2003, 5, 164-168 DOI:10.1039/B304078J (Paper). Supramolecular synthons in phenol–is... more CrystEngComm, 2003, 5, 164-168 DOI:10.1039/B304078J (Paper). Supramolecular synthons in phenol–isonicotinamide adducts. Peddy Vishweshwara, Ashwini Nangia*a and Vincent M. Lynchb. a School of Chemistry, University of Hyderabad, Hyderabad, 500 046, India. ...

Journal of Organic Chemistry, 2002

X-ray crystal structures of pyrazinic acid 1 and isomeric methylpyrazine carboxylic acids 2-4 are... more X-ray crystal structures of pyrazinic acid 1 and isomeric methylpyrazine carboxylic acids 2-4 are analyzed to examine the occurrence of carboxylic acid-pyridine supramolecular synthon V in these heterocyclic acids. Synthon V, assembled by (carboxyl)O-H...N(pyridine) and (pyridine)C-H...O(carbonyl) hydrogen bonds, controls self-assembly in the crystal structures of pyridine and pyrazine monocarboxylic acids. The recurrence of acid-pyridine heterodimer V compared to the more common acid-acid homodimer I in the crystal structures of pyridine and pyrazine monocarboxylic acids is explained by energy computations in the RHF 6-31G* basis set. Both the O-H.N and the C-H...O hydrogen bonds in synthon V result from activated acidic donor and basic acceptor atoms in 1-4. Pyrazine 2,3- and 2,5-dicarboxylic acids 10 and 11 crystallize as dihydrates with a (carboxyl)O-H...O(water) hydrogen bond in synthon VII, a recurring pattern in the diacid structures. In summary, the carboxylic acid group forms an O-H...N hydrogen bond in pyrazine monocarboxylic acids and an O-H...O hydrogen bond in pyrazine dicarboxylic acids. This structural analysis correlates molecular features with supramolecular synthons in pyridine and pyrazine carboxylic acids for future crystal engineering strategies.