Synthesis and structure of 2-amino-4-methyl­pyridin-1-ium hippurate dihydrate

Vetrivel, V.; Marimuthu, N.; Balakrishnan, T.

doi:10.1107/S2056989026004846

research communications

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ISSN: 2056-9890

Volume 82| Part 6| June 2026| Pages 702-706

https://doi.org/10.1107/S2056989026004846

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Synthesis and structure of 2-amino-4-methylpyridin-1-ium hippurate dihydrate

Vanitha Vetrivel,^a Nishandhini Marimuthu ^b ^* and Thangavelu Balakrishnan ^a ^*

^aCrystal Growth Laboratory, PG and Research department of Physics, Thanthai Periyar Government Arts and, Science College (Autonomous), affiliated to Bharathidasan University, Tiruchirappalli, Tiruchirappalli-620 023, Tamil Nadu, India, and ^bDepartment of Bioinformatics, VISTAS, Chennai, Tamil Nadu, India
^*Correspondence e-mail: [email protected], [email protected]

Edited by W. T. A. Harrison, University of Aberdeen, United Kingdom (Received 6 April 2026; accepted 10 May 2026; online 22 May 2026)

In the extended structure of the title salt, C₆H₉N₂⁺·C₉H₈NO₃⁻·2H₂O, the 2-amino-4-methylpyridin-1-ium cation and hippurate [or 2-(phenylformamido)acetate] anion are linked through paired N—H⋯O hydrogen bonds, forming an R₂²(8) motif. The water molecules of crystallization participate in O—H⋯O and N—H⋯O hydrogen-bonding interactions, which connect the molecular components into one-dimensional chains that extend along the [010] direction. These interactions collectively generate a three-dimensional supramolecular network.

Keywords: crystal structure; 2-amino-4-methylpyridin-1-ium cation; hippurate anion; Hirshfeld surface analysis.

CCDC reference: 2552915

1. Chemical context

Pyridinium-based organic salts continue to attract interest owing to their diverse supramolecular architectures and their ability to form robust hydrogen-bonded networks in the solid state (Konovalova & Reiss, 2025 ; Bis & Zaworotko, 2005 ; Budzikur et al., 2022 ). 2-Amino-4-methylpyridine, C₆H₈N₂, is a bi-functional heterocycle containing both a basic pyridine nitrogen (ring N atom) and an exocyclic amino group (-NH₂), enabling different hydrogen-bonding patterns and facilitating salt formation with a variety of organic acids. Protonated aminopyridines are widely used as structure-directing cations because their multiple donor and acceptor sites support extended N—H⋯O, O—H⋯O, and π-associated supramolecular motifs in the solid-state (Bedeković et al., 2017 ; Desiraju, 2002 ; Aakeröy & Seddon, 1993 ).

Hippuric acid (benzoylglycine, C₉H₉NO₃) is a biologically relevant carboxylic acid that mimics short peptide fragments and provides several potential donor/acceptor sites through its carboxyl, amide, and aromatic groups (Li et al., 2024 ). Both hippuric acid and its deprotonated hippurate (benzoylglycinate, C₉H₈NO₃⁻) anions are widely employed in organic salts and co-crystals, where their amide, carboxylate, and aromatic functionalities enable complementary hydrogen-bonding interactions and π-stacking contacts (Laishram et al., 2025 ; Suganya et al., 2021 ).

Proton transfer in crystalline acid–base systems is commonly rationalized using the ΔpK_a rule (Cruz-Cabeza, 2012 , 2022 ): when the difference between the pK_a of the conjugate acid of the base and the pK_a of the acid exceeds ≃ 2–3, salt formation is favored. For the present system, the reported pK_a values (hippuric acid ≃ 3.6 and 2-amino-4-methylpyridinium ion ≃ 7.5–8.1) gives ΔpK_a ≃ 3.9, supporting proton transfer and the formation of a 2-amino-4-methylpyridinium benzoylglycinate salt. Such a proton transfer leads to the formation of charge-assisted N⁺—H⋯O hydrogen bonds, which are typically shorter, and more electrostatically strengthened than their neutral counterparts; these interactions often dominate the molecular packing, enhance crystal cohesion and facilitate the incorporation of water molecules of crystallization that further connect the ions through O—H⋯O and O—H⋯N hydrogen bonding.

As part of our studies in this area, we now describe the synthesis, structure and Hirshfeld surface analysis of the title hydrated salt, C₆H₉N₂⁺·C₉H₈NO₃⁻·2H₂O (I).

2. Structural commentary

The hydrated title salt (I) was obtained by proton transfer from hippuric acid to 2-amino-4-methylpyridine in aqueous solution. The crystal structure unambiguously confirms salt formation through a proton-transfer reaction, which is consistent with the acidity constants of the components noted above, which strongly favors salt formation rather than co-crystallization

Compound (I) crystallizes as orthorhombic in space group Pbca. The asymmetric unit consists of one 2-amino-4-methylpyridin-1-ium cation, one hippurate anion and two water molecules of crystallization, as illustrated in Fig. 1. In the cation, proton migration to the pyridine nitrogen atom (N2) is further supported by the increase in the internal angle around the protonated nitrogen atom [C10—N2—C14 = 122.22 (13)°], compared with 117.3 (1)° in neutral 2-amino-4-methylpyridine (Kvick & Noordik, 1977 ). The bond lengths and angles of the cation closely resemble those observed in related structures, including 2-amino-4-methylpyridin-1-ium hydrogen squarate (Vetrivel et al., 2025 ) and other similar protonated analogues (Khalib et al., 2014 ). The non-hydrogen atoms of the cation are essentially planar, with a maximum deviation of 0.027 (3) Å for atom C15. In the hippurate anion, the carboxylate group has nearly equivalent C—O bond lengths [O2—C9 = 1.2377 (18) Å and O3—C9 = 1.2598 (19) Å; Δ = 0.0221 Å], confirming deprotonation (Table 1). The key torsion angles for the side chain are C1—C7—N1—C8 = −175.96 (12)° and C7—N1—C8—C9 = −87.11 (18)° and the dihedral angle between the C1–C6 phenyl ring and the carboxylate plane (O1/O2/C8/C9) is 70.96 (7)°. These geometric parameters are comparable to those reported for deprotonated hippurate anions in related crystal structures, such as cytosinium N-benzoylglycinate monohydrate (Görbitz & Sagstuen, 2004 ).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O5—H5A⋯O4	0.83 (2)	2.00 (2)	2.8225 (18)	167 (3)
N1—H1⋯O4ⁱ	0.85 (1)	2.25 (2)	2.9992 (18)	148 (2)
N2—H2A⋯O3ⁱⁱ	0.90 (2)	1.78 (2)	2.6850 (17)	176 (2)
N3—H3A⋯O2ⁱⁱ	0.89 (2)	1.99 (2)	2.8751 (17)	175 (2)
N3—H3B⋯O5ⁱⁱⁱ	0.90 (2)	1.94 (2)	2.8368 (18)	171 (2)
O4—H4A⋯O3^iv	0.88 (2)	1.88 (2)	2.7392 (17)	166 (2)
O4—H4B⋯O1^v	0.87 (2)	1.95 (2)	2.8173 (18)	173 (2)
O5—H5B⋯O2ⁱ	0.88 (2)	1.94 (2)	2.8061 (18)	170 (3)
Symmetry codes: (i) ; (ii) $[-x+{\script{1\over 2}}, -y+1, z-{\script{1\over 2}}]$ ; (iii) $[-x+{\script{1\over 2}}, y-{\script{1\over 2}}, z]$ ; (iv) $[x+{\script{1\over 2}}, -y+{\script{3\over 2}}, -z+1]$ ; (v) .

Figure 1
The molecular structure of the title salt, (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level.

3. Supramolecular features

In the extended structure, the cation and anion are connected through N2—H2A⋯O3 and N3—H3A⋯O2 hydrogen bonds (Table 1, Fig. 2), generating an R₂² (8) motif. The two water molecules of crystallization participate actively in the hydrogen-bonding network. In particular, a O5—H5A⋯O4 hydrogen bond links the two water molecules. All the oxygen atoms of the anion (O1–O3), together with the water O atoms (O4 and O5), function as hydrogen-bond acceptors in various intermolecular N—H⋯O and O—H⋯O interactions (Table 1).

Figure 2
(a) Part of the crystal structure of (I) showing the R₂²(8) motif formed by intermolecular N—H⋯O hydrogen bonds. (b) The N1—H1⋯O4 and O4—H4B⋯O1 hydrogen bonds connect neighbouring hippurate anions and water molecule O4 (water – 1), forming a one-dimensional chains runs along the [010] direction. (c) The O4—H4A⋯O3, N1—H1⋯O4 and O4—H4B⋯O1 hydrogen bonds generate an R₄⁴ (16) motif, resulting in a supramolecular ladder-like arrangement running parallel to [010].

The N1—H1⋯O4 and O4—H4B⋯O1 hydrogen bonds connect neighbouring hippurate anions and water molecule (water-1, O4), forming four-membered units that propagate into a one dimensional chains extending along the [010] direction. Furthermore, the O4—H4A⋯O3 hydrogen bond along with the N1—H1⋯O4 and O4—H4B⋯O1 hydrogen bonds, generates an R₄⁴ (16) loop, resulting in a supramolecular ladder-like arrangement running parallel to [010]. This ladder is further reinforced by hydrogen bonding involving the cation, namely N2—H2A⋯O3, N3—H3A⋯O2 and O5—H5B⋯O2 and N3—H3B···O5, which link the second water molecule (water-2, O5) to the cationic fragment. Collectively, the hydrogen bonds interconnect the cations, anions, and water molecules of crystallization into a three-dimensional supramolecular network (Figs. 3 and 4).

Figure 3
Overall crystal packing of the title salt (I), viewed down the a axis. Hydrogen atoms have been omitted for clarity.

Figure 4
Two views of the Hirshfeld surfaces of the cation, anion and water molecules of crystallization in the title salt (I), mapped over d_norm and the shape-index surface.

4. Hirshfeld surface analysis

Hirshfeld surface (HS) analysis was carried out using CrystalExplorer 21.5 (Turner et al., 2017 ). The front and back views of the HS mapped over d_norm for the asymmetric unit are shown in Fig. 4, together with the individual surfaces for the cation, anion and the two water molecules. Bright-red spots on the d_norm-mapped surfaces correspond to close contacts, i.e., intermolecular distances shorter than the sum of the van der Waals radii, and thus indicate significant non-covalent interactions. In contrast, the shape-index surface does not exhibit complementary red and blue triangular features, indicating the absence of significant π–π stacking interactions in (I).

The full and decomposed two-dimensional fingerprint plots for the cation, anion and the water molecules are presented in Fig. 5. The H⋯H contacts make the largest contribution for both the cation (50.1%) and the anion (47.1%), and also account for significant contributions in water-1 (40.6%) and water-2 (46.5%). For the water molecules, O⋯H/H⋯O contacts are particularly prominent, reflecting their active participation in O—H⋯O hydrogen bonds. The sharp spikes observed in the FP plots at d_e + d_i = 1.6–1.8 Å for O⋯H/H⋯O contacts are characteristic of strong N/O—H⋯O hydrogen bonds (Table 1). The C⋯H/H⋯C interactions represent the next significant contribution in the cation (18.5%) and anion (12.8%). The remaining contacts, namely N⋯H/H⋯N, C⋯N and C⋯C, contribute comparatively less to the total Hirshfeld surface area. Although both water molecules participate in O—H⋯O hydrogen bonding, their relative percentage contributions and hydrogen-bond geometries indicate subtle differences in their interaction environments within the crystal.

Figure 5
Full and decomposed two-dimensional fingerprint (FP) plots for the cation, anion and the two water molecules of crystallization in the title salt (I), showing the different intermolecular contacts and their percentage contributions.

5. Database survey

A search of the Cambridge Structural Database (CSD, Version 6.01, updated of November 2025; (Groom et al., 2016 ) performed using Conquest (Bruno et al., 2002 ) for the 2-amino-4-methylpyridin-1-ium cation yielded 62 entries corresponding to salt forms. A number of these salts are with substituted benzoic acids such as 2-hydroxybenzoic acid (CSD refcode DUTZOI) and 3-hydroxybenzoic acid (AGAQIK) (Khalib et al., 2013 ), 2- and 4-chlorobenzoic acids (COZVAQ and COZVOE); 4-methylbenzoic acid (COZVIY) (Khalib et al., 2014); and 4-nitrobenzoic acid (DUNCOF; Hemamalini & Fun, 2010a ), as well as other related substituted benzoates.

Salts with aliphatic carboxylic acids have also been reported, including succinic acid (DICYEW; Seth et al., 2018 ), fumaric acid (DUSPUD; Hemamalini & Fun, 2010c ), trifluoroacetic acid (KUSVAW; Hemamalini & Fun, 2010b ), sorbic acid (SUZXUH; Hemamalini & Fun, 2010d ), oxalic acid (YIZDAQ; Hemalatha et al., 2023 ) and tartaric acid (YOHHIO; Jovita et al., 2014 ).

A separate search for the hippurate anion revealed eight structures in the CSD. These correspond to salts of hippuric acid with various active pharmaceutical ingredients (APIs) and biologically relevant bases, including imatinib (AJIPOC) (Jiang et al., 2025 ); ciprofloxacin (OSUQEA; Chadha et al., 2016 ); cytosine (CYTBGL01); Görbitz & Sagstuen, 2004) guanidine (BEMWOJ; Reena et al., 2022 ) and acridine (XANSOY; Suganya et al., 2021). These results indicate that, although salts of the individual components are well documented in the structural database, structures comprising both components in a single salt are comparatively uncommon. The available entries further underscore the conformational flexibility and supramolecular versatility of the hippurate anion, which consistently assembles into stable crystal architectures primarily via classical N—H⋯O and O—H⋯O hydrogen-bonding interactions.

6. Synthesis and crystallization

Hot methanol solutions (50 mL) of 2-amino-4-methylpyridine (1.08 g, 1.00 mmol) and hippuric acid (1.80 g, 1.00 mmol) were mixed and warmed over a heating magnetic stirrer hotplate for 6h. The reaction mixture was stirred at room temperature for 6 h to obtain a clear homogeneous solution. The resulting solution was filtered and allowed to evaporate slowly at room temperature. Colourless block-shaped crystals suitable for single-crystal X-ray diffraction were obtained after approximately 10 days.

7. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. H atoms were positioned geometrically (C—H = 0.93–0.96 Å) and refined as riding with U_iso(H) = 1.2U_eq(C).

Table 2
Experimental details

Crystal data
Chemical formula	C₆H₉N₂⁺·C₉H₈NO₃⁻·2(H₂O)
M_r	323.35
Crystal system, space group	Orthorhombic, Pbca
Temperature (K)	298
a, b, c (Å)	15.137 (3), 7.3028 (14), 30.583 (6)
V (Å³)	3380.7 (11)
Z	8
Radiation type	Cu Kα
μ (mm⁻¹)	0.81
Crystal size (mm)	0.35 × 0.24 × 0.22

Data collection
Diffractometer	Bruker D8 Venture Diffractometer
Absorption correction	Multi-scan (SADABS; Krause et al., 2015 )
T_min, T_max	0.547, 0.753
No. of measured, independent and observed [I > 2σ(I)] reflections	24560, 3208, 2918
R_int	0.051
(sin θ/λ)_max (Å⁻¹)	0.610

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.053, 0.153, 1.09
No. of reflections	3208
No. of parameters	234
No. of restraints	8
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.20, −0.20
Computer programs: APEX4, SAINT and XPREP (Bruker, 2021 ), SHELXT2014/5 (Sheldrick, 2015a ), SHELXL2014/3 (Sheldrick, 2015b ), ORTEP-3 for Windows (Farrugia, 2012 ), Mercury (Macrae et al., 2020 ) and PLATON (Spek, 2020 ).

Supporting information

CCDC reference: 2552915

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989026004846/hb8212sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989026004846/hb8212Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2056989026004846/hb8212Isup3.cml

checkCIF report

Computing details top

2-Amino-4-methylpyridin-1-ium 2-(phenylformamido)acetate dihydrate top

Crystal data top

C₆H₉N₂⁺·C₉H₈NO₃⁻·2(H₂O)	D_x = 1.271 Mg m⁻³
M_r = 323.35	Cu Kα radiation, λ = 1.54178 Å
Orthorhombic, Pbca	Cell parameters from 7667 reflections
a = 15.137 (3) Å	θ = 4.1–70.0°
b = 7.3028 (14) Å	µ = 0.81 mm⁻¹
c = 30.583 (6) Å	T = 298 K
V = 3380.7 (11) Å³	Block, colourless
Z = 8	0.35 × 0.24 × 0.22 mm
F(000) = 1376

Data collection top

Bruker D8 Venture Diffractometer	2918 reflections with I > 2σ(I)
Radiation source: micro focus sealed tube	R_int = 0.051
φ and ω scans	θ_max = 70.0°, θ_min = 2.9°
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	h = −18→18
T_min = 0.547, T_max = 0.753	k = −8→8
24560 measured reflections	l = −34→37
3208 independent reflections

Refinement top

Refinement on F²	Hydrogen site location: mixed
Least-squares matrix: full	H atoms treated by a mixture of independent and constrained refinement
R[F² > 2σ(F²)] = 0.053	w = 1/[σ²(F_o²) + (0.0923P)² + 0.350P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.153	(Δ/σ)_max = 0.001
S = 1.09	Δρ_max = 0.20 e Å⁻³
3208 reflections	Δρ_min = −0.19 e Å⁻³
234 parameters	Extinction correction: SHELXL2019/2 (Sheldrick 2015b), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
8 restraints	Extinction coefficient: 0.0072 (6)

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
C1	0.52405 (11)	0.6531 (2)	0.55085 (5)	0.0634 (4)
C2	0.57345 (12)	0.5010 (3)	0.56117 (6)	0.0820 (5)
H2	0.553559	0.420177	0.582510	0.098*
C3	0.65265 (14)	0.4676 (3)	0.53993 (7)	0.0976 (6)
H3	0.685875	0.364962	0.547277	0.117*
C4	0.68232 (13)	0.5843 (4)	0.50824 (6)	0.0949 (6)
H4	0.735675	0.561428	0.494186	0.114*
C5	0.63421 (17)	0.7325 (4)	0.49740 (7)	0.0992 (7)
H5	0.654065	0.811233	0.475605	0.119*
C6	0.55571 (15)	0.7679 (3)	0.51848 (7)	0.0886 (5)
H6	0.523277	0.871148	0.510788	0.106*
C7	0.43806 (12)	0.6994 (2)	0.57182 (5)	0.0653 (4)
C8	0.30803 (10)	0.5937 (2)	0.61047 (5)	0.0666 (4)
H8A	0.275980	0.478744	0.609411	0.080*
H8B	0.276331	0.680558	0.592319	0.080*
C9	0.30683 (10)	0.6635 (2)	0.65749 (5)	0.0614 (4)
C10	0.22844 (9)	0.12490 (18)	0.27751 (4)	0.0547 (3)
C11	0.24565 (10)	0.05872 (18)	0.32012 (4)	0.0588 (4)
H11	0.198861	0.022428	0.337826	0.071*
C12	0.32969 (10)	0.0475 (2)	0.33553 (5)	0.0636 (4)
C13	0.40030 (11)	0.1037 (3)	0.30865 (6)	0.0742 (4)
H13	0.458206	0.099824	0.318772	0.089*
C14	0.38185 (11)	0.1635 (3)	0.26776 (6)	0.0743 (5)
H14	0.427978	0.199248	0.249575	0.089*
C15	0.34820 (14)	−0.0249 (3)	0.38085 (6)	0.0892 (6)
H15A	0.365066	0.074466	0.399619	0.134*
H15B	0.395280	−0.112843	0.379533	0.134*
H15C	0.296011	−0.082495	0.392225	0.134*
N1	0.39430 (9)	0.56514 (17)	0.59169 (4)	0.0621 (3)
H1	0.4169 (11)	0.458 (2)	0.5917 (6)	0.074*
N2	0.29813 (8)	0.17252 (17)	0.25277 (4)	0.0623 (3)
H2A	0.2858 (11)	0.212 (2)	0.2254 (5)	0.075*
N3	0.14821 (9)	0.1412 (2)	0.26100 (4)	0.0677 (4)
O1	0.40736 (11)	0.85655 (16)	0.56980 (5)	0.0929 (4)
O2	0.37639 (8)	0.67686 (18)	0.67853 (4)	0.0767 (4)
O3	0.23079 (7)	0.70195 (18)	0.67150 (4)	0.0753 (4)
H3A	0.1393 (13)	0.192 (3)	0.2350 (5)	0.090*
H3B	0.1007 (11)	0.123 (3)	0.2784 (6)	0.090*
O4	0.58180 (8)	0.82361 (16)	0.37897 (4)	0.0752 (4)
H4A	0.6302 (14)	0.835 (3)	0.3632 (7)	0.113*
H4B	0.5816 (16)	0.926 (3)	0.3936 (8)	0.113*
O5	0.48776 (8)	0.5845 (2)	0.32339 (4)	0.0810 (4)
H5A	0.5105 (18)	0.668 (3)	0.3383 (9)	0.122*
H5B	0.5277 (16)	0.498 (3)	0.3257 (9)	0.122*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0790 (9)	0.0570 (8)	0.0541 (7)	−0.0026 (6)	−0.0060 (6)	−0.0066 (6)
C2	0.0823 (11)	0.0888 (12)	0.0747 (10)	0.0142 (9)	0.0078 (8)	0.0155 (9)
C3	0.0814 (11)	0.1203 (17)	0.0911 (13)	0.0221 (11)	0.0085 (10)	0.0122 (12)
C4	0.0799 (11)	0.1351 (19)	0.0696 (10)	−0.0122 (12)	0.0047 (8)	−0.0119 (11)
C5	0.1157 (16)	0.1059 (16)	0.0761 (11)	−0.0271 (14)	0.0145 (11)	0.0030 (11)
C6	0.1159 (15)	0.0685 (10)	0.0816 (11)	−0.0032 (10)	0.0058 (10)	0.0065 (9)
C7	0.0876 (10)	0.0498 (8)	0.0586 (8)	0.0082 (7)	−0.0076 (7)	−0.0093 (6)
C8	0.0699 (9)	0.0698 (9)	0.0602 (8)	0.0084 (7)	−0.0062 (6)	−0.0154 (7)
C9	0.0645 (8)	0.0597 (8)	0.0600 (8)	0.0067 (6)	−0.0044 (6)	−0.0096 (6)
C10	0.0623 (8)	0.0475 (7)	0.0544 (7)	0.0030 (5)	0.0057 (5)	−0.0001 (5)
C11	0.0690 (8)	0.0530 (7)	0.0544 (7)	0.0020 (6)	0.0067 (6)	0.0014 (5)
C12	0.0738 (9)	0.0575 (8)	0.0595 (8)	0.0052 (6)	−0.0026 (6)	−0.0039 (6)
C13	0.0642 (8)	0.0820 (11)	0.0765 (10)	0.0032 (7)	−0.0022 (7)	0.0011 (8)
C14	0.0621 (8)	0.0838 (11)	0.0770 (10)	−0.0003 (7)	0.0113 (7)	0.0041 (8)
C15	0.0932 (12)	0.1075 (14)	0.0669 (10)	0.0085 (11)	−0.0128 (9)	0.0097 (9)
N1	0.0744 (8)	0.0522 (6)	0.0596 (7)	0.0106 (5)	−0.0007 (5)	−0.0081 (5)
N2	0.0652 (7)	0.0642 (7)	0.0574 (7)	0.0041 (5)	0.0092 (5)	0.0053 (5)
N3	0.0623 (7)	0.0802 (9)	0.0607 (7)	0.0035 (6)	0.0047 (5)	0.0136 (6)
O1	0.1266 (11)	0.0521 (7)	0.1000 (9)	0.0204 (6)	0.0054 (8)	−0.0046 (6)
O2	0.0679 (7)	0.0963 (8)	0.0658 (6)	0.0137 (5)	−0.0098 (5)	−0.0226 (5)
O3	0.0647 (7)	0.0951 (8)	0.0660 (6)	0.0101 (5)	−0.0031 (5)	−0.0206 (6)
O4	0.0689 (7)	0.0668 (7)	0.0900 (8)	−0.0026 (5)	0.0090 (6)	−0.0152 (6)
O5	0.0726 (7)	0.0918 (9)	0.0787 (8)	0.0119 (6)	−0.0210 (6)	−0.0044 (6)

Geometric parameters (Å, º) top

C1—C2	1.376 (2)	C10—N2	1.3439 (18)
C1—C6	1.383 (3)	C10—C11	1.4142 (19)
C1—C7	1.490 (2)	C11—C12	1.359 (2)
C2—C3	1.385 (3)	C11—H11	0.9300
C2—H2	0.9300	C12—C13	1.409 (2)
C3—C4	1.367 (3)	C12—C15	1.510 (2)
C3—H3	0.9300	C13—C14	1.354 (3)
C4—C5	1.346 (3)	C13—H13	0.9300
C4—H4	0.9300	C14—N2	1.349 (2)
C5—C6	1.376 (3)	C14—H14	0.9300
C5—H5	0.9300	C15—H15A	0.9600
C6—H6	0.9300	C15—H15B	0.9600
C7—O1	1.2394 (19)	C15—H15C	0.9600
C7—N1	1.330 (2)	N1—H1	0.851 (14)
C8—N1	1.442 (2)	N2—H2A	0.904 (15)
C8—C9	1.526 (2)	N3—H3A	0.888 (15)
C8—H8A	0.9700	N3—H3B	0.903 (15)
C8—H8B	0.9700	O4—H4A	0.881 (17)
C9—O2	1.2377 (18)	O4—H4B	0.872 (17)
C9—O3	1.2598 (19)	O5—H5A	0.834 (17)
C10—N3	1.3205 (19)	O5—H5B	0.879 (17)

C2—C1—C6	117.73 (17)	N3—C10—C11	123.54 (13)
C2—C1—C7	124.01 (14)	N2—C10—C11	117.56 (13)
C6—C1—C7	118.25 (15)	C12—C11—C10	120.83 (13)
C1—C2—C3	120.33 (18)	C12—C11—H11	119.6
C1—C2—H2	119.8	C10—C11—H11	119.6
C3—C2—H2	119.8	C11—C12—C13	119.33 (14)
C4—C3—C2	120.5 (2)	C11—C12—C15	120.87 (15)
C4—C3—H3	119.8	C13—C12—C15	119.79 (16)
C2—C3—H3	119.8	C14—C13—C12	118.45 (16)
C5—C4—C3	119.9 (2)	C14—C13—H13	120.8
C5—C4—H4	120.0	C12—C13—H13	120.8
C3—C4—H4	120.0	N2—C14—C13	121.56 (15)
C4—C5—C6	120.2 (2)	N2—C14—H14	119.2
C4—C5—H5	119.9	C13—C14—H14	119.2
C6—C5—H5	119.9	C12—C15—H15A	109.5
C5—C6—C1	121.4 (2)	C12—C15—H15B	109.5
C5—C6—H6	119.3	H15A—C15—H15B	109.5
C1—C6—H6	119.3	C12—C15—H15C	109.5
O1—C7—N1	121.22 (17)	H15A—C15—H15C	109.5
O1—C7—C1	121.09 (16)	H15B—C15—H15C	109.5
N1—C7—C1	117.66 (13)	C7—N1—C8	121.76 (13)
N1—C8—C9	115.75 (12)	C7—N1—H1	118.4 (13)
N1—C8—H8A	108.3	C8—N1—H1	119.7 (13)
C9—C8—H8A	108.3	C10—N2—C14	122.22 (13)
N1—C8—H8B	108.3	C10—N2—H2A	116.2 (11)
C9—C8—H8B	108.3	C14—N2—H2A	121.6 (11)
H8A—C8—H8B	107.4	C10—N3—H3A	121.3 (13)
O2—C9—O3	125.66 (13)	C10—N3—H3B	119.6 (13)
O2—C9—C8	120.40 (13)	H3A—N3—H3B	117.8 (19)
O3—C9—C8	113.94 (13)	H4A—O4—H4B	102 (2)
N3—C10—N2	118.90 (13)	H5A—O5—H5B	101 (3)

C6—C1—C2—C3	0.9 (3)	N3—C10—C11—C12	−179.07 (14)
C7—C1—C2—C3	179.70 (18)	N2—C10—C11—C12	1.2 (2)
C1—C2—C3—C4	−0.6 (3)	C10—C11—C12—C13	0.4 (2)
C2—C3—C4—C5	−0.3 (3)	C10—C11—C12—C15	−179.38 (15)
C3—C4—C5—C6	0.7 (3)	C11—C12—C13—C14	−1.5 (2)
C4—C5—C6—C1	−0.4 (3)	C15—C12—C13—C14	178.29 (17)
C2—C1—C6—C5	−0.5 (3)	C12—C13—C14—N2	1.0 (3)
C7—C1—C6—C5	−179.33 (17)	O1—C7—N1—C8	2.2 (2)
C2—C1—C7—O1	161.68 (17)	C1—C7—N1—C8	−175.96 (12)
C6—C1—C7—O1	−19.5 (2)	C9—C8—N1—C7	−87.11 (18)
C2—C1—C7—N1	−20.2 (2)	N3—C10—N2—C14	178.47 (15)
C6—C1—C7—N1	158.64 (15)	C11—C10—N2—C14	−1.8 (2)
N1—C8—C9—O2	−6.4 (2)	C13—C14—N2—C10	0.7 (3)
N1—C8—C9—O3	174.15 (14)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O5—H5A···O4	0.83 (2)	2.00 (2)	2.8225 (18)	167 (3)
N1—H1···O4ⁱ	0.85 (1)	2.25 (2)	2.9992 (18)	148 (2)
N2—H2A···O3ⁱⁱ	0.90 (2)	1.78 (2)	2.6850 (17)	176 (2)
N3—H3A···O2ⁱⁱ	0.89 (2)	1.99 (2)	2.8751 (17)	175 (2)
N3—H3B···O5ⁱⁱⁱ	0.90 (2)	1.94 (2)	2.8368 (18)	171 (2)
O4—H4A···O3^iv	0.88 (2)	1.88 (2)	2.7392 (17)	166 (2)
O4—H4B···O1^v	0.87 (2)	1.95 (2)	2.8173 (18)	173 (2)
O5—H5B···O2ⁱ	0.88 (2)	1.94 (2)	2.8061 (18)	170 (3)

Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x+1/2, −y+1, z−1/2; (iii) −x+1/2, y−1/2, z; (iv) x+1/2, −y+3/2, −z+1; (v) −x+1, −y+2, −z+1.

Acknowledgements

The authors gratefully acknowledge SAIF, IIT Madras, for the SCXRD data collection.

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