Synthesis, crystal structure and characterization of a three-dimensional Cd^II coordination polymer constructed from 2,5-bis­(1H-1,2,4-triazol-1-yl)terephthalate

Bifunctional organic ligands are very popular for the design of coordination polymers because they allow the formation of a great diversity of structures. In the title coordination polymer, the new bifunctional inversion-symmetric ligand 2,5-bis­(1H-1,2,4-triazol-1-yl)terephthalic acid (abbreviated as H₂bttpa) links Cd^II cations, giving rise to the three-dimensional Cd^II coordination polymer catena-poly[di­aqua­[μ₄-2,5-bis­(1H-1,2,4-triazol-1-yl)terephthalato-κ⁴O¹:O⁴:N⁴:N^4′]cadmium(II)], [Cd(C₁₂H₆N₆O₄)(H₂O)₂]_n or [Cd(bttpa)(H₂O)₂]_n. The asymmetric unit consists of half a Cd^II cation, half a bttpa²⁻ ligand and one coordinated water mol­ecule. The Cd^II cation is located on a twofold axis and is hexa­coordinated in a distorted octa­hedral environment of four O and two N atoms. Four different bttpa²⁻ ligands contribute to this coordination, with two carboxyl­ate O atoms in trans positions and two triazole N atoms in cis positions. Two aqua ligands in cis positions complete the coordination sphere. The fully deprotonated bttpa²⁻ ligand sits about a crystallographic centre of inversion and links two Cd^II cations to form a chain in a μ₂-terephthalato-κ²O¹:O⁴ bridge. This chain extends in the other two directions via the triazole heterocycles, producing a three-dimensional framework. O—H...O hydrogen bonds and weak C—H...N inter­actions stabilize the three-dimensional crystal structure. The FT–IR spectrum, X-ray powder pattern, thermogravimetric behaviour and solid-state photoluminescence of the title polymer have been investigated. The photoluminescence is enhanced and red-shifted with respect to the uncoordinated ligand.

Computing details

Data collection: APEX2 (Bruker, 2000); cell refinement: SAINT (Bruker, 2000); data reduction: SAINT (Bruker, 2000); program(s) used to solve structure: SHELXLT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015b); molecular graphics: SHELXTL (Sheldrick, 2008) and DIAMOND (Brandenburg, 2005); software used to prepare material for publication: publCIF (Westrip, 2010).

catena-Poly[diaqua[µ₄-2,5-bis(1H-1,2,4-triazol-1-yl)terephthalato-κ⁴O¹:O⁴:N⁴:N^4']cadmium(II)]

Crystal data

[Cd(C12H6N6O4)(H2O)2]	F(000) = 880
Mr = 446.66	Dx = 2.000 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 20.0932 (9) Å	Cell parameters from 5786 reflections
b = 7.1128 (3) Å	θ = 3.0–28.2°
c = 10.4548 (4) Å	µ = 1.52 mm^−1
β = 96.857 (1)°	T = 298 K
V = 1483.50 (11) Å^3	Rhombic, white
Z = 4	0.20 × 0.20 × 0.10 mm

Data collection

Bruker APEXII CCD diffractometer	1734 reflections with I > 2σ(I)
φ and ω scans	Rint = 0.022
Absorption correction: multi-scan (SADABS; Bruker, 2000)	θmax = 28.3°, θmin = 3.0°
Tmin = 0.683, Tmax = 0.746	h = −26→26
6888 measured reflections	k = −9→9
1816 independent reflections	l = −12→13

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	Hydrogen site location: mixed
R[F^2 > 2σ(F^2)] = 0.016	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.039	w = 1/[σ^2(Fo^2) + (0.0178P)^2 + 1.1701P] where P = (Fo^2 + 2Fc^2)/3
S = 1.10	(Δ/σ)max < 0.001
1816 reflections	Δρmax = 0.39 e Å^−3
122 parameters	Δρmin = −0.35 e Å^−3

Special details

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.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > 2sigma(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Cd1	0.0000	0.14436 (2)	0.2500	0.01513 (5)
O1	0.08596 (5)	0.15441 (16)	0.11747 (11)	0.0245 (2)
O2	0.16855 (6)	0.0854 (3)	0.27234 (14)	0.0495 (4)
O3	0.06470 (6)	−0.09414 (18)	0.35380 (13)	0.0290 (3)
H3A	0.0691 (14)	−0.114 (3)	0.438 (3)	0.053 (8)*
H3B	0.1051 (15)	−0.048 (4)	0.333 (3)	0.071 (9)*
N1	0.13667 (6)	0.48158 (18)	−0.01553 (12)	0.0186 (2)
N2	0.11585 (8)	0.5724 (2)	0.08670 (13)	0.0295 (3)
N3	0.05439 (7)	0.65764 (18)	−0.09719 (13)	0.0235 (3)
C1	0.19361 (7)	0.3595 (2)	−0.00502 (14)	0.0188 (3)
C2	0.19957 (7)	0.2079 (2)	0.07980 (14)	0.0193 (3)
C3	0.25735 (7)	0.0986 (2)	0.08314 (15)	0.0220 (3)
H3	0.2630	−0.0039	0.1386	0.026*
C4	0.14741 (8)	0.1455 (2)	0.16448 (16)	0.0228 (3)
C5	0.09981 (7)	0.5340 (2)	−0.12351 (15)	0.0224 (3)
H5	0.1052	0.4901	−0.2054	0.027*
C6	0.06632 (9)	0.6767 (2)	0.03246 (17)	0.0300 (4)
H6	0.0416	0.7566	0.0790	0.036*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cd1	0.01299 (7)	0.01765 (8)	0.01486 (8)	0.000	0.00206 (5)	0.000
O1	0.0152 (5)	0.0374 (6)	0.0222 (6)	0.0029 (4)	0.0072 (4)	0.0039 (5)
O2	0.0217 (6)	0.0955 (12)	0.0323 (7)	0.0056 (7)	0.0079 (5)	0.0338 (8)
O3	0.0262 (6)	0.0321 (6)	0.0287 (7)	0.0042 (5)	0.0036 (5)	0.0099 (5)
N1	0.0164 (5)	0.0239 (6)	0.0165 (6)	0.0071 (5)	0.0059 (5)	0.0034 (5)
N2	0.0330 (7)	0.0379 (8)	0.0184 (7)	0.0151 (6)	0.0065 (6)	0.0004 (6)
N3	0.0211 (6)	0.0271 (7)	0.0231 (7)	0.0087 (5)	0.0050 (5)	0.0047 (5)
C1	0.0139 (6)	0.0242 (7)	0.0190 (7)	0.0069 (5)	0.0044 (5)	0.0037 (5)
C2	0.0139 (6)	0.0259 (7)	0.0190 (7)	0.0040 (5)	0.0059 (5)	0.0050 (5)
C3	0.0174 (7)	0.0268 (7)	0.0229 (7)	0.0060 (6)	0.0070 (6)	0.0100 (6)
C4	0.0166 (6)	0.0312 (8)	0.0221 (7)	0.0047 (6)	0.0086 (6)	0.0075 (6)
C5	0.0218 (7)	0.0270 (8)	0.0184 (7)	0.0079 (6)	0.0024 (6)	0.0015 (6)
C6	0.0329 (9)	0.0348 (9)	0.0234 (8)	0.0168 (7)	0.0081 (7)	0.0014 (6)

Geometric parameters (Å, º)

Cd1—N3^i	2.3051 (13)	N2—C6	1.314 (2)
Cd1—N3^ii	2.3051 (13)	N3—C5	1.3200 (19)
Cd1—O3^iii	2.3256 (12)	N3—C6	1.355 (2)
Cd1—O3	2.3256 (12)	N3—Cd1^ii	2.3051 (13)
Cd1—O1^iii	2.3408 (11)	C1—C3^iv	1.385 (2)
Cd1—O1	2.3408 (11)	C1—C2	1.392 (2)
O1—C4	1.2750 (19)	C2—C3	1.394 (2)
O2—C4	1.233 (2)	C2—C4	1.517 (2)
O3—H3A	0.88 (3)	C3—C1^iv	1.385 (2)
O3—H3B	0.92 (3)	C3—H3	0.9300
N1—C5	1.3274 (19)	C5—H5	0.9300
N1—N2	1.3570 (18)	C6—H6	0.9300
N1—C1	1.4299 (17)
N3^i—Cd1—N3^ii	104.68 (7)	C6—N2—N1	102.56 (13)
N3^i—Cd1—O3^iii	164.04 (5)	C5—N3—C6	103.35 (13)
N3^ii—Cd1—O3^iii	85.98 (5)	C5—N3—Cd1^ii	123.03 (11)
N3^i—Cd1—O3	85.98 (5)	C6—N3—Cd1^ii	130.17 (11)
N3^ii—Cd1—O3	164.04 (5)	C3^iv—C1—C2	121.92 (13)
O3^iii—Cd1—O3	86.32 (7)	C3^iv—C1—N1	116.31 (13)
N3^i—Cd1—O1^iii	83.88 (4)	C2—C1—N1	121.77 (13)
N3^ii—Cd1—O1^iii	93.98 (4)	C1—C2—C3	117.13 (13)
O3^iii—Cd1—O1^iii	83.55 (4)	C1—C2—C4	125.82 (13)
O3—Cd1—O1^iii	99.03 (4)	C3—C2—C4	116.98 (13)
N3^i—Cd1—O1	93.98 (4)	C1^iv—C3—C2	120.95 (14)
N3^ii—Cd1—O1	83.88 (4)	C1^iv—C3—H3	119.5
O3^iii—Cd1—O1	99.03 (4)	C2—C3—H3	119.5
O3—Cd1—O1	83.55 (4)	O2—C4—O1	125.57 (14)
O1^iii—Cd1—O1	176.50 (6)	O2—C4—C2	116.66 (14)
C4—O1—Cd1	121.29 (10)	O1—C4—C2	117.74 (13)
Cd1—O3—H3A	124.3 (17)	N3—C5—N1	109.83 (14)
Cd1—O3—H3B	95.2 (18)	N3—C5—H5	125.1
H3A—O3—H3B	108 (2)	N1—C5—H5	125.1
C5—N1—N2	110.06 (12)	N2—C6—N3	114.19 (14)
C5—N1—C1	126.57 (13)	N2—C6—H6	122.9
N2—N1—C1	123.20 (12)	N3—C6—H6	122.9
C5—N1—N2—C6	0.07 (19)	Cd1—O1—C4—C2	−162.87 (10)
C1—N1—N2—C6	175.63 (15)	C1—C2—C4—O2	−143.50 (18)
C5—N1—C1—C3^iv	50.1 (2)	C3—C2—C4—O2	39.5 (2)
N2—N1—C1—C3^iv	−124.72 (17)	C1—C2—C4—O1	38.4 (2)
C5—N1—C1—C2	−130.37 (17)	C3—C2—C4—O1	−138.58 (16)
N2—N1—C1—C2	54.8 (2)	C6—N3—C5—N1	0.21 (18)
C3^iv—C1—C2—C3	0.0 (3)	Cd1^ii—N3—C5—N1	161.12 (10)
N1—C1—C2—C3	−179.53 (14)	N2—N1—C5—N3	−0.19 (19)
C3^iv—C1—C2—C4	−177.03 (16)	C1—N1—C5—N3	−175.56 (14)
N1—C1—C2—C4	3.4 (2)	N1—N2—C6—N3	0.1 (2)
C1—C2—C3—C1^iv	0.0 (3)	C5—N3—C6—N2	−0.2 (2)
C4—C2—C3—C1^iv	177.30 (15)	Cd1^ii—N3—C6—N2	−159.15 (13)
Cd1—O1—C4—O2	19.3 (2)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C6—H6···O3^v	0.93	2.56	3.428 (2)	156
C5—H5···N2^vi	0.93	2.25	3.176 (2)	172
O3—H3B···O2	0.92 (3)	1.77 (3)	2.6711 (19)	165 (3)
O3—H3A···O1^vii	0.88 (3)	1.89 (3)	2.7720 (18)	175 (3)

Symmetry codes: (v) −x, y+1, −z+1/2; (vi) x, −y+1, z−1/2; (vii) x, −y, z+1/2.