Synthesis and structure of a binuclear calcium nitrate coordination complex with bridging zwitterionic nicotinic acid

Burkitbaeva, G.; Djumanazarova, Z.; Bektursinova, A.; Ashurov, J.; Kadirova, S.; Choriev, O.; Meldebekova, S.; Torambetov, B.

doi:10.1107/S2056989026001271

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ISSN: 2056-9890

Volume 82| Part 3| March 2026| Pages 278-281

https://doi.org/10.1107/S2056989026001271

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Synthesis and structure of a binuclear calcium nitrate coordination complex with bridging zwitterionic nicotinic acid

Gulmira Burkitbaeva,^a Zulfiya Djumanazarova,^a Aysanem Bektursinova,^a Jamshid Ashurov,^b Shakhnoza Kadirova,^c Odil Choriev,^b Saule Meldebekova ^a and Batirbay Torambetov ^c ^*

^aKarakalpak State University, 1 Ch.Abdirov St. Nukus, 230112, Uzbekistan, ^bInstitute of Bioorganic Chemistry, Academy of Sciences of Uzbekistan, M., Ulugbek, St, 83, Tashkent, 100125, Uzbekistan, and ^cNational University of Uzbekistan named after Mirzo Ulugbek, 4 University St., Tashkent, 100174, Uzbekistan
^*Correspondence e-mail: [email protected]

Edited by W. T. A. Harrison, University of Aberdeen, United Kingdom (Received 26 January 2026; accepted 5 February 2026; online 13 February 2026)

The title coordination complex, bis(μ-pyridin-1-ium-3-carboxylato-κ²O:O′)bis[diaquabis(nitrato-κ²O,O′)calcium(II)], [Ca₂(C₆H₅NO₂)₂(NO₃)₄(H₂O)₄], was prepared from calcium nitrate and nicotinic acid in a water–ethanol solvent mixture. The asymmetric unit contains a half molecule of the complex, with the calcium atom exhibiting a coordination number of eight, forming a distorted dodecahedral geometry with a mixed-ligand environment. The μ₂-O,O′ bridging zwitterionic nicotinic acid molecules generate a centrosymmetric dinuclear complex. The extended structure features N—H⋯O, O—H⋯O and C—H⋯O hydrogen bonds, which generate a three-dimensional network. Hirshfeld surface and two-dimensional fingerprint plot analyses were performed to quantify and visualize the intermolecular interactions contributing to the overall cohesion of the structure.

Keywords: crystal structure; calcium; nicotinic acid; Hirshfeld surface analysis.

CCDC reference: 2529092

1. Chemical context

Nicotinic acid (C₆H₅NO₂; niacin or vitamin B₃) is an essential nutrient that plays a crucial role in human metabolism. It is used as a dietary supplement and is also utilized therapeutically for the management of coronary heart diseases (Malik & Kashyap, 2003 ). Clinically, nicotinic acid is primarily prescribed to regulate elevated cholesterol levels and provides several additional pharmacological benefits (Carlson, 2005 ). Furthermore, it has been demonstrated to decrease the incidence and severity of cardiovascular events as well as overall mortality (Canner et al., 1986 ). Structurally, nicotinic acid contains a nitrogen atom within the pyridine ring and a carboxylic acid (–COOH) functional group, allowing it to coordinate with metal ions through multiple donor sites (Zhou & Wang, 2015 ; Cherkasova et al., 2018 ). Under certain conditions, the pyridine nitrogen atom can become protonated, while the carboxylic acid group loses a proton, resulting in the formation of the zwitterionic form of the ligand (Iqbal et al., 2021 ). In the present study, we describe the utilization of nicotinic acid in the synthesis of a coordination complex of calcium, [Ca₂(C₆H₅NO₂)₂(H₂O)₄(NO₃)₄], (I).

2. Structural commentary

Single-crystal X-ray diffraction analysis revealed that (I) crystallizes in the triclinic system in space group P $[\overline{1}]$ . The asymmetric unit contains half of the complex, in which the central calcium atom is coordinated by two nitrate anions in a bidentate fashion, two aqua ligands, and two unidentate carboxylate O atoms, resulting in a coordination number of eight and forming a distorted dodecahedral geometry with a mixed-ligand structure. The nicotinate ligand exists in its zwitterionic form, where the pyridine nitrogen atom N1 is protonated and the deprotonated carboxylate group [C6—O1 = 1.259 (3) Å. C6—O2 = 1.241 (3) Å, O1—C6—O2 = 123.94 (19)°] coordinates through both oxygen atoms to two calcium centers [Ca1⋯Ca1ⁱ = 4.3188 (5) Å; symmetry code: (i) 1 − x, 1 − y, −z] thereby acting as a μ₂-O,O′ bridging ligand (Fig. 1). The Ca—O bond lengths (Table 1) for the carboxylate ligands (O1 and O2) are the shortest, indicating the strongest coordination to the metal centre. The Ca—O bonds for the aqua ligands (O1W and O2W) are slightly longer, while the longest Ca—O bonds (O3, O5, O6, O7) are observed in the bidentate nitrate ligands, where electron delocalization in the N—O bonds of the nitrate ions reduces the donor ability of oxygen atoms and weakens the Ca—O interactions.

Table 1
Selected bond lengths (Å)

Ca1—O1ⁱ	2.4020 (15)	Ca1—O3	2.5810 (16)
Ca1—O1W	2.4426 (15)	Ca1—O5	2.4990 (16)
Ca1—O2	2.3314 (15)	Ca1—O6	2.5116 (17)
Ca1—O2W	2.3927 (15)	Ca1—O7	2.6680 (17)
Symmetry code: (i) .

Figure 1
The molecular structure of (I) with displacement ellipsoids shown at the 50% probability level. Symmetry code (i) 1 − x, 1 − y, −z.

3. Supramolecular features

As a result of the presence of numerous acceptor oxygen atoms, the title complex exhibits various hydrogen-bonding interactions, including N—H⋯O, O—H⋯O and C—H⋯O types (Table 2). The molecular packing viewed along the b-axis direction (Fig. 2) reveals that two molecular units of the complex are connected through O—H⋯O interactions extending along the a-axis direction. Along the b-axis, the molecules are further linked through C—H⋯O and O—H⋯O interactions. The coordinated water molecules also participate in hydrogen bonding with oxygen atoms from the nitrate anions and the carboxylate groups, as well as with phenyl C—H groups, forming O—H⋯O and C—H⋯O linkages (Table 2). Along the c-axis direction, the crystal packing features N—H⋯O and several C—H⋯O interactions, involving the nitrate oxygen atoms as acceptors and phenyl or amine hydrogen atoms as donors. The C—H⋯O interactions involving the nitrate oxygens and aromatic C—H groups form a one-dimensional assembly along the c-axis direction. Collectively, these hydrogen-bonding interactions generate a three-dimensional supramolecular network.

Table 2
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1W—H1WA⋯O8ⁱⁱ	0.85	2.14	2.955 (3)	160
O1W—H1WB⋯O1ⁱⁱⁱ	0.85	1.88	2.723 (2)	173
O2W—H2WA⋯O1Wⁱ	0.88	2.35	2.887 (2)	119
O2W—H2WB⋯O1^iv	0.88	2.43	3.268 (2)	158
O2W—H2WB⋯O7^v	0.88	2.32	2.897 (2)	123
N1—H1⋯O4^vi	0.86	1.98	2.782 (2)	155
C2—H2⋯O2Wⁱⁱ	0.93	2.40	3.327 (2)	175
C3—H3⋯O3^vi	0.93	2.45	3.228 (3)	141
C4—H4⋯O4^vii	0.93	2.46	3.102 (3)	127
Symmetry codes: (i) ; (ii) ; (iii) ; (iv) ; (v) ; (vi) ; (vii) .

Figure 2
Visualization of the packing in (I) viewed along the b-axis direction, showing the CaO₈ moieties and polyhedra and C—H⋯O, O—H⋯O and N–H⋯O interactions as blue dashed lines.

4. Hirshfeld Surface Analysis

The intermolecular interactions contributing to the stability of the complex were analyzed using Hirshfeld surface and fingerprint plot analysis implemented in CrystalExplorer (Spackman et al., 2021 ). The analysis revealed that O⋯H/H⋯O interactions are predominant, constituting 63.2% of the total intermolecular contacts. This predominance arises from the abundance of oxygen atoms derived from nitrate anions, coordinated water molecules, and carboxylate groups. These interactions are visualized as intense red spots on the Hirshfeld surface. Other notable interactions include N⋯H/H⋯N (4.3%), C⋯H/H⋯C (5.1%), H⋯H (12.1%), and C⋯O/O⋯C (10.3%) contacts, together accounting for approximately 95% of the total surface interactions. Additionally, the O⋯H/H⋯O interactions appear as two sharp spikes at d_e + d_i = 1.8 Å in the corresponding fingerprint plot (Fig. 3).

Figure 3
The Hirshfeld surface and corresponding two-dimensional fingerprint plots for (I).

5. Database survey

A survey of the Cambridge Structural Database (CSD, Version 6.01, November 2025; Groom et al., 2016 ) revealed 209 crystal structures containing nicotinic acid ligands exhibiting an O₂ coordination mode. Among these, thirteen structures feature the ligand in a zwitterionic form, wherein the pyridine nitrogen atom is protonated while coordination to the metal occurs through deprotonated carboxylate oxygen atoms (O₂ coordination set). The reported metal atoms in such complexes include Sc⁺³ (refcode AFIMIO, Cherkasova et al., 2018), Cr⁺³ (BONTED, Gonzalez-Vergara et al., 1982 ), Eu⁺³ (DEYLOJ, Lu et al., 2007 ; XOYQIM, Kong et al., 2009 ), Ce⁺³ (DEYLUP, Lu et al., 2007), Fe⁺³ (INOBET, Chen, 2010 ; SINZAS, Chen et al., 2013 ), Mo⁺⁶ (IZASUX, Chen et al., 2004 ; JEPNEX, Cotton et al., 1990 ), Al⁺³ (RIWCUZ, RIWCUZ01, Zhao et al., 2024 ), U⁺⁶ (SUZREN, Andreev et al., 2020 ), and Gd⁺³ (XOYQOS, Kong et al., 2009). Thus it may be seen that no crystal structure containing calcium ions coordinated by a zwitterionic nicotinic acid ligand has been reported to date.

6. Synthesis and crystallization

Ca(NO₃)₂·4H₂O (0.236 g, 1.00 mmol) was added under continuous stirring to a solution of nicotinic acid (0.123 g, 1.00 mmol) dissolved in 10 ml of ethanol–water (50:50). The resulting colorless solution was stirred for 3 h and was then left to stand at room temperature. After two weeks, colorless blocks suitable for X-ray diffraction were obtained (yield 70%) by the slow evaporation of the solvent.

7. Refinement details

Crystal data, data collection and structure refinement details are summarized in Table 3. H atoms were positioned geometrically (O—H = 0.85–0.88, N—H = 0.96, C—H = 0.93 Å) and refined as riding with U_iso(H) = 1.2U_eq(N, C) or 1.5U_eq(O).

Table 3
Experimental details

Crystal data
Chemical formula	[Ca₂(C₆H₅NO₂)₂(NO₃)₄(H₂O)₄]
M_r	646.48
Crystal system, space group	Triclinic, P $[\overline{1}]$
Temperature (K)	293
a, b, c (Å)	7.2785 (2), 7.7034 (2), 11.8102 (2)
α, β, γ (°)	76.204 (2), 88.236 (2), 67.828 (2)
V (Å³)	594.24 (3)
Z	1
Radiation type	Cu Kα
μ (mm⁻¹)	5.19
Crystal size (mm)	0.3 × 0.2 × 0.12

Data collection
Diffractometer	XtaLAB Synergy, Single source at home/near, HyPix3000
Absorption correction	Multi-scan (CrysAlis PRO; Rigaku OD, 2023 )
T_min, T_max	0.522, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections	5079, 2278, 2204
R_int	0.025
(sin θ/λ)_max (Å⁻¹)	0.615

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.036, 0.096, 1.09
No. of reflections	2278
No. of parameters	183
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.38, −0.50
Computer programs: CrysAlis PRO (Rigaku OD, 2023), SHELXT2018/2 (Sheldrick, 2015a ), SHELXL2016/6 (Sheldrick, 2015b ) and OLEX2 (Dolomanov et al., 2009 ).

Supporting information

CCDC reference: 2529092

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989026001271/hb8192sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989026001271/hb8192Isup2.hkl

checkCIF report

Computing details top

Bis(µ-pyridin-1-ium-3-carboxylato-κ²O:O')bis[diaqua\ bis(nitrato-κ²O,O')calcium(II)] top

Crystal data top

[Ca₂(C₆H₅NO₂)₂(NO₃)₄(H₂O)₄]	Z = 1
M_r = 646.48	F(000) = 332
Triclinic, P1	D_x = 1.807 Mg m⁻³
a = 7.2785 (2) Å	Cu Kα radiation, λ = 1.54184 Å
b = 7.7034 (2) Å	Cell parameters from 4225 reflections
c = 11.8102 (2) Å	θ = 3.9–71.3°
α = 76.204 (2)°	µ = 5.19 mm⁻¹
β = 88.236 (2)°	T = 293 K
γ = 67.828 (2)°	Block, colourless
V = 594.24 (3) Å³	0.3 × 0.2 × 0.12 mm

Data collection top

XtaLAB Synergy, Single source at home/near, HyPix3000 diffractometer	2278 independent reflections
Radiation source: micro-focus sealed X-ray tube, PhotonJet (Cu) X-ray Source	2204 reflections with I > 2σ(I)
Mirror monochromator	R_int = 0.025
Detector resolution: 10.0000 pixels mm^-1	θ_max = 71.5°, θ_min = 3.9°
ω scans	h = −8→8
Absorption correction: multi-scan (CrysAlisPro; Rigaku OD, 2023)	k = −9→9
T_min = 0.522, T_max = 1.000	l = −14→11
5079 measured reflections

Refinement top

Refinement on F²	Primary atom site location: dual
Least-squares matrix: full	Hydrogen site location: mixed
R[F² > 2σ(F²)] = 0.036	H-atom parameters constrained
wR(F²) = 0.096	w = 1/[σ²(F_o²) + (0.0521P)² + 0.3004P] where P = (F_o² + 2F_c²)/3
S = 1.09	(Δ/σ)_max < 0.001
2278 reflections	Δρ_max = 0.38 e Å⁻³
183 parameters	Δρ_min = −0.50 e Å⁻³
0 restraints

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
Ca1	0.65567 (5)	0.56954 (5)	0.12434 (3)	0.02000 (14)
O1	0.2555 (2)	0.2795 (2)	0.05968 (12)	0.0302 (3)
O1W	0.8866 (2)	0.2683 (2)	0.08421 (13)	0.0281 (3)
H1WA	0.893487	0.174012	0.141145	0.042*
H1WB	1.003606	0.268073	0.082744	0.042*
O2	0.4355 (2)	0.4144 (2)	0.12536 (14)	0.0324 (4)
O2W	0.3380 (2)	0.8281 (2)	0.07100 (13)	0.0291 (3)
H2WA	0.220459	0.819656	0.071424	0.044*
H2WB	0.312208	0.952976	0.046846	0.044*
O3	0.7743 (3)	0.3173 (2)	0.32194 (14)	0.0393 (4)
O4	0.7352 (3)	0.3969 (2)	0.48750 (13)	0.0438 (5)
O5	0.5874 (3)	0.6076 (2)	0.32756 (13)	0.0364 (4)
O6	0.9434 (3)	0.6251 (2)	0.19867 (17)	0.0413 (4)
O7	0.6916 (2)	0.8917 (2)	0.14747 (15)	0.0370 (4)
O8	0.9511 (3)	0.8834 (3)	0.2375 (2)	0.0575 (6)
N1	0.2536 (3)	−0.0327 (3)	0.39757 (16)	0.0298 (4)
H1	0.245919	−0.144565	0.412136	0.036*
N2	0.6989 (3)	0.4398 (3)	0.38014 (15)	0.0287 (4)
N3	0.8640 (3)	0.8012 (3)	0.19526 (16)	0.0290 (4)
C1	0.3034 (3)	0.2220 (3)	0.26437 (17)	0.0204 (4)
C2	0.2854 (3)	0.0452 (3)	0.28886 (18)	0.0250 (4)
H2	0.295230	−0.019107	0.230181	0.030*
C3	0.2331 (4)	0.0548 (3)	0.48484 (19)	0.0326 (5)
H3	0.207827	−0.003366	0.558899	0.039*
C4	0.2493 (4)	0.2298 (4)	0.46462 (19)	0.0343 (5)
H4	0.234927	0.292264	0.524625	0.041*
C5	0.2876 (3)	0.3141 (3)	0.35361 (18)	0.0267 (4)
H5	0.302616	0.431917	0.339274	0.032*
C6	0.3352 (3)	0.3123 (3)	0.14110 (17)	0.0223 (4)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Ca1	0.0215 (2)	0.0201 (2)	0.0190 (2)	−0.00918 (16)	0.00170 (15)	−0.00375 (15)
O1	0.0331 (8)	0.0423 (9)	0.0198 (7)	−0.0199 (7)	0.0031 (6)	−0.0070 (6)
O1W	0.0244 (7)	0.0268 (8)	0.0319 (8)	−0.0090 (6)	0.0007 (6)	−0.0060 (6)
O2	0.0316 (8)	0.0311 (8)	0.0384 (9)	−0.0195 (7)	0.0072 (7)	−0.0036 (7)
O2W	0.0283 (8)	0.0235 (7)	0.0343 (8)	−0.0089 (6)	−0.0003 (6)	−0.0065 (6)
O3	0.0587 (11)	0.0265 (8)	0.0288 (8)	−0.0102 (8)	0.0019 (7)	−0.0094 (6)
O4	0.0831 (14)	0.0328 (9)	0.0200 (8)	−0.0297 (9)	−0.0021 (8)	−0.0014 (6)
O5	0.0499 (10)	0.0243 (8)	0.0262 (8)	−0.0077 (7)	0.0056 (7)	−0.0015 (6)
O6	0.0329 (9)	0.0264 (8)	0.0605 (11)	−0.0073 (7)	−0.0070 (8)	−0.0084 (8)
O7	0.0322 (9)	0.0299 (8)	0.0406 (9)	−0.0067 (7)	−0.0033 (7)	−0.0013 (7)
O8	0.0685 (14)	0.0548 (12)	0.0676 (13)	−0.0425 (11)	−0.0096 (11)	−0.0156 (10)
N1	0.0372 (10)	0.0196 (8)	0.0311 (9)	−0.0131 (8)	0.0017 (8)	0.0002 (7)
N2	0.0429 (11)	0.0241 (9)	0.0218 (8)	−0.0177 (8)	0.0019 (8)	−0.0022 (7)
N3	0.0337 (10)	0.0277 (9)	0.0287 (9)	−0.0166 (8)	0.0015 (8)	−0.0041 (7)
C1	0.0177 (9)	0.0211 (9)	0.0215 (9)	−0.0067 (7)	0.0001 (7)	−0.0043 (7)
C2	0.0273 (10)	0.0221 (10)	0.0257 (10)	−0.0095 (8)	0.0024 (8)	−0.0062 (8)
C3	0.0379 (12)	0.0354 (12)	0.0220 (10)	−0.0149 (10)	0.0036 (9)	−0.0012 (9)
C4	0.0470 (14)	0.0368 (12)	0.0228 (10)	−0.0180 (11)	0.0031 (9)	−0.0107 (9)
C5	0.0326 (11)	0.0227 (10)	0.0279 (10)	−0.0134 (9)	−0.0003 (8)	−0.0071 (8)
C6	0.0191 (9)	0.0203 (9)	0.0248 (10)	−0.0060 (7)	0.0026 (7)	−0.0032 (7)

Geometric parameters (Å, º) top

Ca1—O1ⁱ	2.4020 (15)	O3—N2	1.248 (2)
Ca1—O1W	2.4426 (15)	O4—N2	1.242 (2)
Ca1—O2ⁱ	3.0060 (17)	O5—N2	1.254 (2)
Ca1—O2	2.3314 (15)	O6—N3	1.249 (2)
Ca1—O2W	2.3927 (15)	O7—N3	1.255 (3)
Ca1—O3	2.5810 (16)	O8—N3	1.234 (3)
Ca1—O5	2.4990 (16)	N1—H1	0.8600
Ca1—O6	2.5116 (17)	N1—C2	1.335 (3)
Ca1—O7	2.6680 (17)	N1—C3	1.336 (3)
Ca1—N2	2.9335 (17)	C1—C2	1.379 (3)
Ca1—N3	3.0034 (18)	C1—C5	1.384 (3)
Ca1—C6ⁱ	3.055 (2)	C1—C6	1.508 (3)
O1—C6	1.259 (3)	C2—H2	0.9300
O1W—H1WA	0.8508	C3—H3	0.9300
O1W—H1WB	0.8506	C3—C4	1.361 (3)
O2—C6	1.241 (3)	C4—H4	0.9300
O2W—H2WA	0.8821	C4—C5	1.388 (3)
O2W—H2WB	0.8820	C5—H5	0.9300

O1ⁱ—Ca1—O1W	84.73 (5)	Ca1—O2W—H2WA	127.6
O1ⁱ—Ca1—O2ⁱ	46.53 (4)	Ca1—O2W—H2WB	127.8
O1ⁱ—Ca1—O3	147.44 (6)	H2WA—O2W—H2WB	104.6
O1ⁱ—Ca1—O5	142.29 (6)	N2—O3—Ca1	93.43 (12)
O1ⁱ—Ca1—O6	81.75 (6)	N2—O5—Ca1	97.23 (12)
O1ⁱ—Ca1—O7	72.20 (5)	N3—O6—Ca1	100.57 (13)
O1W—Ca1—O2ⁱ	73.14 (5)	N3—O7—Ca1	92.80 (12)
O1W—Ca1—O3	72.44 (5)	C2—N1—H1	118.5
O1W—Ca1—O5	122.30 (5)	C2—N1—C3	123.07 (19)
O1W—Ca1—O6	89.72 (5)	C3—N1—H1	118.5
O1W—Ca1—O7	133.97 (5)	O3—N2—Ca1	61.43 (10)
O2—Ca1—O1ⁱ	119.02 (5)	O3—N2—O5	118.50 (17)
O2—Ca1—O1W	81.19 (5)	O4—N2—Ca1	171.39 (15)
O2—Ca1—O2ⁱ	72.65 (5)	O4—N2—O3	120.76 (19)
O2—Ca1—O2W	75.77 (5)	O4—N2—O5	120.74 (19)
O2—Ca1—O3	80.76 (6)	O5—N2—Ca1	57.68 (10)
O2—Ca1—O5	92.75 (6)	O6—N3—Ca1	55.29 (10)
O2—Ca1—O6	156.07 (6)	O6—N3—O7	117.38 (18)
O2—Ca1—O7	144.83 (6)	O7—N3—Ca1	62.53 (11)
O2W—Ca1—O1ⁱ	84.04 (5)	O8—N3—Ca1	172.48 (16)
O2W—Ca1—O1W	145.16 (5)	O8—N3—O6	121.4 (2)
O2W—Ca1—O2ⁱ	75.22 (5)	O8—N3—O7	121.2 (2)
O2W—Ca1—O3	127.68 (6)	C2—C1—C5	118.86 (18)
O2W—Ca1—O5	84.95 (5)	C2—C1—C6	119.50 (17)
O2W—Ca1—O6	120.97 (5)	C5—C1—C6	121.63 (18)
O2W—Ca1—O7	72.40 (5)	N1—C2—C1	119.38 (19)
O3—Ca1—O2ⁱ	139.04 (5)	N1—C2—H2	120.3
O3—Ca1—O7	107.41 (5)	C1—C2—H2	120.3
O5—Ca1—O2ⁱ	157.64 (5)	N1—C3—H3	120.2
O5—Ca1—O3	50.05 (5)	N1—C3—C4	119.6 (2)
O5—Ca1—O6	73.43 (6)	C4—C3—H3	120.2
O5—Ca1—O7	70.09 (5)	C3—C4—H4	120.3
O6—Ca1—O2ⁱ	125.81 (5)	C3—C4—C5	119.4 (2)
O6—Ca1—O3	75.39 (6)	C5—C4—H4	120.3
O6—Ca1—O7	48.68 (5)	C1—C5—C4	119.71 (19)
O7—Ca1—O2ⁱ	112.33 (5)	C1—C5—H5	120.1
C6—O1—Ca1ⁱ	109.07 (12)	C4—C5—H5	120.1
Ca1—O1W—H1WA	109.4	O1—C6—Ca1ⁱ	48.00 (10)
Ca1—O1W—H1WB	109.5	O1—C6—C1	117.01 (17)
H1WA—O1W—H1WB	104.5	O2—C6—Ca1ⁱ	75.99 (12)
Ca1—O2—Ca1ⁱ	107.35 (5)	O2—C6—O1	123.94 (19)
C6—O2—Ca1ⁱ	80.40 (12)	O2—C6—C1	119.05 (18)
C6—O2—Ca1	170.25 (14)	C1—C6—Ca1ⁱ	164.88 (13)

Ca1ⁱ—O1—C6—O2	2.9 (2)	C2—N1—C3—C4	−1.6 (4)
Ca1ⁱ—O1—C6—C1	−177.59 (13)	C2—C1—C5—C4	−1.6 (3)
Ca1ⁱ—O2—C6—O1	−2.24 (19)	C2—C1—C6—Ca1ⁱ	25.7 (6)
Ca1ⁱ—O2—C6—C1	178.29 (17)	C2—C1—C6—O1	32.5 (3)
Ca1—O3—N2—O4	−170.42 (18)	C2—C1—C6—O2	−148.0 (2)
Ca1—O3—N2—O5	8.8 (2)	C3—N1—C2—C1	1.7 (3)
Ca1—O5—N2—O3	−9.1 (2)	C3—C4—C5—C1	1.7 (4)
Ca1—O5—N2—O4	170.07 (18)	C5—C1—C2—N1	−0.1 (3)
Ca1—O6—N3—O7	−7.8 (2)	C5—C1—C6—Ca1ⁱ	−153.0 (4)
Ca1—O6—N3—O8	171.91 (19)	C5—C1—C6—O1	−146.1 (2)
Ca1—O7—N3—O6	7.25 (19)	C5—C1—C6—O2	33.4 (3)
Ca1—O7—N3—O8	−172.5 (2)	C6—C1—C2—N1	−178.77 (18)
N1—C3—C4—C5	−0.2 (4)	C6—C1—C5—C4	177.1 (2)

Symmetry code: (i) −x+1, −y+1, −z.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O1W—H1WA···O8ⁱⁱ	0.85	2.14	2.955 (3)	160
O1W—H1WB···O1ⁱⁱⁱ	0.85	1.88	2.723 (2)	173
O2W—H2WA···O1Wⁱ	0.88	2.35	2.887 (2)	119
O2W—H2WB···O1^iv	0.88	2.43	3.268 (2)	158
O2W—H2WB···O7^v	0.88	2.32	2.897 (2)	123
N1—H1···O4^vi	0.86	1.98	2.782 (2)	155
C2—H2···O2Wⁱⁱ	0.93	2.40	3.327 (2)	175
C3—H3···O3^vi	0.93	2.45	3.228 (3)	141
C4—H4···O4^vii	0.93	2.46	3.102 (3)	127

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

Acknowledgements

BT would like to acknowledge the FAIRE programme provided by the Cambridge Crystallographic Data Centre (CCDC) for the use of the Cambridge Structural Database (CSD) and associated software.

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research communications\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

Synthesis and structure of a binuclear calcium nitrate coordination complex with bridging zwitterionic nicotinic acid

1. Chemical context

2. Structural commentary

3. Supra­molecular features

4. Hirshfeld Surface Analysis

5. Database survey

6. Synthesis and crystallization

7. Refinement details

Supporting information

Acknowledgements

References

research communications

3. Supramolecular features