A fourfold inter­penetrating cadmium(II) metal–organic framework based on 2,4,6-tris­(pyri­din-4-yl)-1,3,5-triazine with reversible photochromic properties

2,4,6-Tris(pyridin-4-yl)-1,3,5-triazine (tpt), as an organic mol­ecule with an electron-deficient nature, has attracted considerable inter­est because of its photoinduced electron transfer from neutral organic molecules to form stable anionic radicals. This makes it an excellent candidate as an organic linker in the construction of photochromic complexes. Such a photochromic three-dimensional (3D) metal–organic framework (MOF) has been prepared using this ligand. Crystallization of tpt with Cd(NO₃)₂·4H₂O in an N,N-di­methyl­acetamide–methanol mixed-solvent system under solvothermal conditions afforded the 3D MOF poly[[bis­(nitrato-κ²O,O′)cadmium(II)]-μ₃-2,4,6-tris­(pyridin-4-yl)-1,3,5-tri­azine-κ³N²:N⁴:N⁶], [Cd(NO₃)₂(C₁₈H₁₂N₆)]_n, which was characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis and single-crystal X-ray diffraction. The X-ray diffraction crystal structure analysis reveals that the asymmetric unit contains one independent Cd^II cation, one tpt ligand and two coordinated NO₃⁻ anions. The Cd^II cations are connected by tpt ligands to generate a 3D framework. The single framework leaves voids that are filled by mutual inter­penetration of three independent equivalent frameworks in a fourfold inter­penetrating architecture. The compound shows a good thermal stability and exhibits a reversible photochromic behaviour, which may originate from the photoinduced electron-transfer generation of radicals in the tpt ligand.

Computing details

Data collection: APEX2 (Bruker, 2004); cell refinement: APEX2 (Bruker, 2004); data reduction: APEX2 (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: DIAMOND (Brandenburg, 2010); software used to prepare material for publication: publCIF (Westrip, 2010).

Poly[[bis(nitrato-κ²O,O')cadmium(II)]-µ₃-2,4,6-tris(pyridin-4-yl)-1,3,5-triazine-κ³N²:N⁴:N⁶]

Crystal data

[Cd(NO3)2(C18H12N6)]	Dx = 1.675 Mg m^−3
Mr = 548.76	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pbcn	Cell parameters from 9256 reflections
a = 27.1721 (15) Å	θ = 2.6–30.6°
b = 9.7995 (6) Å	µ = 1.06 mm^−1
c = 16.3477 (9) Å	T = 153 K
V = 4353.0 (4) Å^3	Block, yellow
Z = 8	0.35 × 0.21 × 0.08 mm
F(000) = 2176

Data collection

Bruker APEXII area-detector diffractometer	3574 reflections with I > 2σ(I)
w scan	Rint = 0.075
Absorption correction: multi-scan (SADABS; Bruker, 2004)	θmax = 26.4°, θmin = 2.2°
Tmin = 0.780, Tmax = 1.000	h = −33→33
31963 measured reflections	k = −11→11
4374 independent reflections	l = −20→19

Refinement

Refinement on F^2	1 restraint
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.029	H-atom parameters constrained
wR(F^2) = 0.072	w = 1/[σ^2(Fo^2) + 2.0785P] where P = (Fo^2 + 2Fc^2)/3
S = 1.03	(Δ/σ)max = 0.004
4374 reflections	Δρmax = 0.56 e Å^−3
298 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.

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

	x	y	z	Uiso*/Ueq
Cd1	0.62048 (2)	0.30439 (2)	0.55738 (2)	0.02439 (8)
O1	0.58275 (8)	0.2351 (2)	0.43176 (12)	0.0444 (5)
O2	0.56869 (7)	0.44534 (19)	0.46411 (12)	0.0370 (5)
O3	0.52776 (8)	0.3505 (3)	0.36422 (14)	0.0618 (6)
O4	0.65396 (8)	0.0797 (2)	0.56422 (14)	0.0466 (5)
O5	0.67216 (9)	0.2049 (2)	0.66839 (14)	0.0548 (6)
O6	0.70668 (8)	0.0058 (2)	0.65510 (16)	0.0686 (7)
N1	0.62853 (8)	0.5041 (2)	0.63114 (15)	0.0356 (6)
N2	0.45547 (8)	1.2258 (2)	0.89434 (13)	0.0305 (5)
N3	0.80789 (8)	1.1364 (2)	0.98532 (13)	0.0293 (5)
N4	0.59350 (7)	0.9351 (2)	0.78449 (12)	0.0263 (5)
N5	0.63505 (8)	1.0824 (2)	0.87707 (13)	0.0288 (5)
N6	0.67771 (7)	0.8927 (2)	0.81879 (12)	0.0266 (5)
N7	0.55910 (9)	0.3437 (3)	0.41864 (14)	0.0386 (6)
N8	0.67827 (9)	0.0937 (3)	0.63030 (18)	0.0464 (7)
C1	0.58912 (11)	0.5826 (3)	0.6446 (2)	0.0492 (8)
H1	0.5587	0.5561	0.6208	0.059*
C2	0.59025 (11)	0.6996 (3)	0.6911 (2)	0.0456 (8)
H2	0.5612	0.7517	0.6991	0.055*
C3	0.63421 (9)	0.7405 (3)	0.72590 (15)	0.0270 (6)
C4	0.67637 (10)	0.6625 (3)	0.71059 (17)	0.0321 (6)
H4	0.7075	0.6892	0.7318	0.039*
C5	0.67167 (10)	0.5456 (3)	0.66383 (17)	0.0352 (6)
H5	0.7002	0.4918	0.6542	0.042*
C6	0.63565 (9)	0.8637 (3)	0.77891 (15)	0.0248 (5)
C7	0.59467 (9)	1.0388 (2)	0.83766 (15)	0.0259 (5)
C8	0.67576 (9)	1.0059 (2)	0.86447 (15)	0.0250 (5)
C9	0.54687 (9)	1.1067 (3)	0.85634 (15)	0.0282 (6)
C10	0.50313 (10)	1.0321 (3)	0.85235 (19)	0.0388 (7)
H10	0.5037	0.9390	0.8361	0.047*
C11	0.45885 (10)	1.0945 (3)	0.87221 (18)	0.0404 (7)
H11	0.4296	1.0417	0.8700	0.049*
C12	0.49819 (11)	1.2958 (3)	0.8999 (2)	0.0435 (8)
H12	0.4969	1.3884	0.9172	0.052*
C13	0.54401 (10)	1.2398 (3)	0.88174 (19)	0.0400 (7)
H13	0.5730	1.2932	0.8869	0.048*
C14	0.72180 (9)	1.0508 (2)	0.90573 (15)	0.0264 (6)
C15	0.72012 (10)	1.1495 (3)	0.96686 (18)	0.0382 (7)
H15	0.6897	1.1897	0.9824	0.046*
C16	0.76343 (11)	1.1878 (3)	1.00446 (19)	0.0418 (8)
H16	0.7618	1.2547	1.0465	0.050*
C17	0.80924 (10)	1.0419 (3)	0.92681 (18)	0.0398 (7)
H17	0.8402	1.0039	0.9124	0.048*
C18	0.76774 (10)	0.9963 (3)	0.88588 (17)	0.0369 (7)
H18	0.7705	0.9284	0.8446	0.044*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cd1	0.01702 (12)	0.02431 (14)	0.03183 (12)	−0.00204 (7)	0.00356 (7)	−0.00266 (8)
O1	0.0413 (13)	0.0449 (12)	0.0470 (12)	0.0125 (10)	−0.0078 (9)	−0.0156 (10)
O2	0.0341 (12)	0.0338 (11)	0.0432 (11)	0.0002 (8)	−0.0017 (9)	−0.0004 (9)
O3	0.0423 (14)	0.0897 (17)	0.0534 (14)	0.0160 (12)	−0.0206 (11)	−0.0114 (13)
O4	0.0305 (13)	0.0413 (12)	0.0680 (15)	0.0074 (9)	0.0011 (10)	0.0056 (10)
O5	0.0543 (15)	0.0638 (16)	0.0463 (13)	0.0074 (11)	−0.0030 (10)	0.0131 (11)
O6	0.0434 (14)	0.0728 (16)	0.0895 (18)	0.0215 (12)	0.0133 (13)	0.0482 (14)
N1	0.0237 (12)	0.0357 (14)	0.0475 (14)	0.0008 (9)	−0.0007 (10)	−0.0137 (11)
N2	0.0197 (12)	0.0291 (13)	0.0427 (13)	0.0011 (9)	0.0017 (10)	−0.0059 (10)
N3	0.0233 (12)	0.0274 (12)	0.0371 (13)	−0.0021 (9)	−0.0068 (9)	0.0015 (10)
N4	0.0216 (12)	0.0292 (12)	0.0281 (11)	0.0016 (9)	−0.0020 (9)	−0.0034 (10)
N5	0.0220 (11)	0.0306 (12)	0.0337 (12)	0.0007 (9)	−0.0023 (9)	−0.0058 (10)
N6	0.0213 (11)	0.0288 (12)	0.0298 (11)	−0.0005 (9)	−0.0021 (9)	−0.0035 (9)
N7	0.0242 (13)	0.0547 (17)	0.0369 (13)	0.0046 (11)	−0.0008 (10)	−0.0047 (12)
N8	0.0269 (14)	0.0479 (17)	0.0644 (18)	0.0048 (12)	0.0168 (13)	0.0243 (15)
C1	0.0245 (16)	0.0508 (19)	0.072 (2)	0.0076 (13)	−0.0127 (14)	−0.0315 (17)
C2	0.0271 (17)	0.0440 (19)	0.066 (2)	0.0097 (12)	−0.0136 (14)	−0.0263 (15)
C3	0.0238 (14)	0.0273 (14)	0.0300 (13)	0.0002 (11)	−0.0022 (10)	−0.0030 (11)
C4	0.0205 (14)	0.0363 (16)	0.0396 (15)	0.0019 (11)	−0.0042 (11)	−0.0110 (12)
C5	0.0220 (14)	0.0354 (16)	0.0483 (17)	0.0034 (11)	−0.0015 (12)	−0.0118 (13)
C6	0.0201 (13)	0.0269 (14)	0.0274 (13)	0.0008 (10)	0.0013 (10)	−0.0006 (11)
C7	0.0237 (14)	0.0270 (14)	0.0269 (13)	0.0004 (10)	−0.0014 (10)	−0.0004 (11)
C8	0.0192 (13)	0.0272 (14)	0.0286 (13)	−0.0014 (10)	0.0013 (10)	0.0007 (11)
C9	0.0238 (14)	0.0308 (15)	0.0301 (13)	0.0016 (11)	−0.0015 (11)	−0.0056 (11)
C10	0.0231 (15)	0.0317 (16)	0.0617 (19)	−0.0019 (11)	0.0002 (13)	−0.0186 (14)
C11	0.0234 (15)	0.0425 (18)	0.0555 (18)	−0.0024 (12)	0.0025 (13)	−0.0198 (15)
C12	0.0274 (17)	0.0285 (16)	0.075 (2)	0.0004 (12)	0.0077 (15)	−0.0114 (15)
C13	0.0184 (15)	0.0320 (16)	0.070 (2)	−0.0011 (11)	0.0071 (13)	−0.0091 (15)
C14	0.0217 (14)	0.0280 (14)	0.0294 (13)	−0.0016 (10)	−0.0007 (10)	0.0021 (11)
C15	0.0211 (15)	0.0431 (17)	0.0503 (17)	0.0001 (12)	−0.0035 (12)	−0.0153 (15)
C16	0.0302 (17)	0.0444 (19)	0.0508 (18)	0.0067 (12)	−0.0102 (13)	−0.0182 (14)
C17	0.0222 (15)	0.0499 (19)	0.0474 (17)	0.0018 (13)	−0.0025 (12)	−0.0094 (15)
C18	0.0244 (15)	0.0439 (17)	0.0425 (16)	0.0003 (12)	−0.0028 (12)	−0.0132 (13)

Geometric parameters (Å, º)

Cd1—N1	2.309 (2)	C1—C2	1.376 (4)
Cd1—N2^i	2.340 (2)	C1—H1	0.9500
Cd1—N3^ii	2.348 (2)	C2—C3	1.383 (4)
Cd1—O4	2.385 (2)	C2—H2	0.9500
Cd1—O1	2.3937 (19)	C3—C4	1.400 (4)
Cd1—O2	2.4927 (19)	C3—C6	1.486 (4)
Cd1—O5	2.493 (2)	C4—C5	1.383 (4)
O1—N7	1.262 (3)	C4—H4	0.9500
O2—N7	1.269 (3)	C5—H5	0.9500
O3—N7	1.233 (3)	C7—C9	1.491 (3)
O4—N8	1.274 (3)	C8—C14	1.488 (3)
O5—N8	1.266 (3)	C9—C13	1.371 (4)
O6—N8	1.226 (3)	C9—C10	1.397 (4)
N1—C1	1.337 (3)	C10—C11	1.389 (4)
N1—C5	1.351 (3)	C10—H10	0.9500
N2—C11	1.339 (3)	C11—H11	0.9500
N2—C12	1.352 (3)	C12—C13	1.393 (4)
N2—Cd1^iii	2.340 (2)	C12—H12	0.9500
N3—C17	1.332 (3)	C13—H13	0.9500
N3—C16	1.346 (4)	C14—C15	1.391 (4)
N3—Cd1^iv	2.348 (2)	C14—C18	1.396 (4)
N4—C7	1.337 (3)	C15—C16	1.380 (4)
N4—C6	1.346 (3)	C15—H15	0.9500
N5—C7	1.342 (3)	C16—H16	0.9500
N5—C8	1.352 (3)	C17—C18	1.385 (4)
N6—C8	1.339 (3)	C17—H17	0.9500
N6—C6	1.346 (3)	C18—H18	0.9500
N1—Cd1—N2^i	100.75 (8)	C2—C3—C4	118.3 (2)
N1—Cd1—N3^ii	88.51 (8)	C2—C3—C6	119.9 (2)
N2^i—Cd1—N3^ii	169.02 (8)	C4—C3—C6	121.8 (2)
N1—Cd1—O4	136.21 (8)	C5—C4—C3	118.4 (2)
N2^i—Cd1—O4	90.96 (7)	C5—C4—H4	120.8
N3^ii—Cd1—O4	86.29 (7)	C3—C4—H4	120.8
N1—Cd1—O1	136.81 (8)	N1—C5—C4	123.2 (2)
N2^i—Cd1—O1	79.52 (8)	N1—C5—H5	118.4
N3^ii—Cd1—O1	89.70 (7)	C4—C5—H5	118.4
O4—Cd1—O1	86.65 (7)	N4—C6—N6	125.5 (2)
N1—Cd1—O2	84.44 (7)	N4—C6—C3	116.1 (2)
N2^i—Cd1—O2	83.73 (7)	N6—C6—C3	118.4 (2)
N3^ii—Cd1—O2	91.39 (7)	N4—C7—N5	125.0 (2)
O4—Cd1—O2	139.07 (7)	N4—C7—C9	116.8 (2)
O1—Cd1—O2	52.46 (7)	N5—C7—C9	118.1 (2)
N1—Cd1—O5	84.16 (8)	N6—C8—N5	125.2 (2)
N2^i—Cd1—O5	97.04 (8)	N6—C8—C14	117.7 (2)
N3^ii—Cd1—O5	89.71 (8)	N5—C8—C14	117.1 (2)
O4—Cd1—O5	52.41 (8)	C13—C9—C10	117.6 (2)
O1—Cd1—O5	138.99 (8)	C13—C9—C7	122.4 (2)
O2—Cd1—O5	168.52 (7)	C10—C9—C7	119.9 (2)
N7—O1—Cd1	97.15 (15)	C11—C10—C9	119.7 (2)
N7—O2—Cd1	92.26 (14)	C11—C10—H10	120.1
N8—O4—Cd1	97.94 (17)	C9—C10—H10	120.1
N8—O5—Cd1	93.01 (17)	N2—C11—C10	123.1 (2)
C1—N1—C5	117.2 (2)	N2—C11—H11	118.5
C1—N1—Cd1	119.85 (18)	C10—C11—H11	118.5
C5—N1—Cd1	122.93 (17)	N2—C12—C13	123.6 (2)
C11—N2—C12	116.6 (2)	N2—C12—H12	118.2
C11—N2—Cd1^iii	117.89 (17)	C13—C12—H12	118.2
C12—N2—Cd1^iii	124.57 (17)	C9—C13—C12	119.4 (2)
C17—N3—C16	116.9 (2)	C9—C13—H13	120.3
C17—N3—Cd1^iv	120.62 (17)	C12—C13—H13	120.3
C16—N3—Cd1^iv	122.35 (18)	C15—C14—C18	117.5 (2)
C7—N4—C6	114.8 (2)	C15—C14—C8	120.2 (2)
C7—N5—C8	114.8 (2)	C18—C14—C8	122.2 (2)
C8—N6—C6	114.3 (2)	C16—C15—C14	118.8 (3)
O3—N7—O1	121.3 (3)	C16—C15—H15	120.6
O3—N7—O2	121.5 (3)	C14—C15—H15	120.6
O1—N7—O2	117.2 (2)	N3—C16—C15	124.1 (3)
O6—N8—O5	121.6 (3)	N3—C16—H16	118.0
O6—N8—O4	122.1 (3)	C15—C16—H16	118.0
O5—N8—O4	116.2 (2)	N3—C17—C18	123.3 (3)
N1—C1—C2	123.5 (3)	N3—C17—H17	118.4
N1—C1—H1	118.2	C18—C17—H17	118.4
C2—C1—H1	118.2	C17—C18—C14	119.5 (3)
C1—C2—C3	119.2 (3)	C17—C18—H18	120.3
C1—C2—H2	120.4	C14—C18—H18	120.3
C3—C2—H2	120.4

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