High-pressure study of a 3d–4f heterometallic CuEu–organic skeleton

We prepared a 3d–4f heterobimetallic CuEu–organic framework NBU-8 with a density of 1921 kg m⁻³ belonging to the family of dense packing materials (dense metal–organic frameworks or MOFs). This MOF material was prepared from 4-(py­rimi­din-5-yl)ben­zoic acid (HPBA) with a bifunctional ligand site as a tripodal ligand and Cu²⁺ and Eu³⁺ as the metal centres; the mol­ecular formula is Cu₃Eu₂(PBA)₆(NO₃)₆·H₂O. This material is a very promising di­methyl­for­m­amide (DMF) mol­ecular chemical sensor. Systematic high-pressure studies of NBU-8 were carried out by powder X-ray diffraction, high-pressure X-ray diffraction and mol­ecular dynamics simulation. The high-pressure experiment shows that the (006) diffraction peak of the crystal structure moves toward a low angle with increasing pressure, accompanied by the phenomenon that the d-spacing increases, and as the pressure increases, the (10) diffraction peak moves to a higher angle, the amplitude of the d-spacing is significantly reduced and finally merges with the (006) diffraction peak into one peak. The amplitude of the d-spacing is significantly reduced, indicating that NBU-8 com­presses and deforms along the a-axis direction when subjected to uniform pressure. This is caused by tilting of the ligands to become more vertical along the c direction, leading to its expansion. This allows greater contraction along the a direction. We also carried out a Rietveld structure refinement and a Birch–Murnaghan solid-state equation fitting for the high-pressure experimental results. We calculated the bulk modulus of the material to be 45.68 GPa, which is consistent with the calculated results. The framework is among the most rigid MOFs reported to date, exceeding that of Cu–BTC. Mol­ecular dynamics simulations estimated that the mechanical energy absorbed by the system when pressurized to 5.128 GPa was 249.261 kcal mol⁻¹. The present work will provide fresh ideas for the study of mechanical energy in other materials.

Computing details

(I)

Crystal data

C66H44Cu3Eu2N18O31	Dx = 1.921 Mg m^−3
Mr = 2079.73	Mo Kα radiation, λ = 0.71073 Å
Trigonal, R3c	Cell parameters from 4858 reflections
a = 14.0021 (3) Å	θ = 2.9–26.1°
c = 63.523 (3) Å	µ = 2.70 mm^−1
V = 10785.7 (5) Å^3	T = 296 K
Z = 6	Brick, blue
F(000) = 6162	0.25 × 0.23 × 0.20 mm

Data collection

CCD area detector diffractometer	2373 independent reflections
Radiation source: fine-focus sealed tube	2002 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.047
phi and ω scans	θmax = 26.1°, θmin = 1.9°
Absorption correction: multi-scan Sheldrick, G. M.. SADABS	h = −17→14
Tmin = 0.659, Tmax = 0.745	k = −17→17
21300 measured reflections	l = −78→65

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.030	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.091	H-atom parameters constrained
S = 1.08	w = 1/[σ^2(Fo^2) + (0.0569P)^2 + 20.0828P] where P = (Fo^2 + 2Fc^2)/3
2373 reflections	(Δ/σ)max < 0.001
180 parameters	Δρmax = 2.15 e Å^−3
0 restraints	Δρmin = −0.59 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
Eu1	1.0000	0.0000	0.075327 (4)	0.02052 (13)
Cu1	1.0000	0.37628 (4)	0.2500	0.02130 (17)
N1	0.9450 (2)	0.2460 (2)	0.22993 (4)	0.0241 (6)
N2	0.8518 (3)	0.0527 (3)	0.22484 (5)	0.0469 (10)
N3	0.8745 (3)	−0.2084 (3)	0.05255 (6)	0.0338 (8)
C1	1.0971 (3)	0.2270 (3)	0.11008 (5)	0.0216 (7)
C2	1.0514 (3)	0.2191 (3)	0.13157 (5)	0.0221 (7)
C3	0.9584 (3)	0.1229 (3)	0.13794 (5)	0.0286 (8)
H3A	0.9197	0.0670	0.1282	0.034*
C4	0.9224 (3)	0.1088 (3)	0.15859 (6)	0.0294 (8)
H4A	0.8604	0.0432	0.1626	0.035*
C5	0.9774 (3)	0.1907 (3)	0.17335 (5)	0.0229 (7)
C6	1.0691 (3)	0.2882 (3)	0.16693 (6)	0.0348 (9)
H6A	1.1062	0.3448	0.1766	0.042*
C7	1.1062 (3)	0.3027 (3)	0.14626 (5)	0.0306 (8)
H7A	1.1678	0.3686	0.1422	0.037*
C8	0.9432 (3)	0.1740 (3)	0.19581 (5)	0.0248 (7)
C9	0.8809 (4)	0.0704 (3)	0.20466 (6)	0.0412 (11)
H9A	0.8579	0.0094	0.1960	0.049*
C10	0.8846 (4)	0.1413 (3)	0.23663 (6)	0.0357 (10)
H10A	0.8642	0.1304	0.2507	0.043*
C11	0.9723 (3)	0.2605 (3)	0.20960 (5)	0.0245 (7)
H11A	1.0127	0.3321	0.2045	0.029*
O1	1.0467 (2)	0.1468 (2)	0.09779 (4)	0.0377 (7)
O2	1.1875 (2)	0.3124 (2)	0.10583 (4)	0.0259 (5)
O3	0.9371 (2)	−0.1995 (2)	0.06795 (4)	0.0350 (6)
O4	0.8741 (2)	−0.1208 (2)	0.04757 (4)	0.0383 (7)
O5	0.8196 (3)	−0.2949 (3)	0.04348 (6)	0.0617 (10)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Eu1	0.02541 (15)	0.02541 (15)	0.01072 (18)	0.01271 (8)	0.000	0.000
Cu1	0.0318 (3)	0.0254 (2)	0.0088 (3)	0.01592 (17)	−0.0010 (2)	−0.00049 (11)
N1	0.0315 (16)	0.0256 (15)	0.0143 (13)	0.0136 (13)	0.0033 (12)	0.0008 (11)
N2	0.073 (3)	0.0261 (18)	0.0212 (16)	0.0094 (19)	0.0104 (17)	0.0038 (14)
N3	0.0319 (17)	0.033 (2)	0.0339 (19)	0.0141 (16)	0.0010 (15)	−0.0067 (15)
C1	0.0302 (19)	0.0273 (19)	0.0127 (16)	0.0185 (16)	0.0000 (14)	−0.0006 (14)
C2	0.0290 (18)	0.0288 (18)	0.0134 (15)	0.0181 (16)	0.0001 (13)	−0.0012 (13)
C3	0.031 (2)	0.031 (2)	0.0163 (17)	0.0094 (16)	−0.0001 (14)	−0.0081 (15)
C4	0.0299 (19)	0.0263 (18)	0.0197 (18)	0.0048 (16)	0.0045 (15)	−0.0020 (14)
C5	0.0323 (19)	0.0267 (18)	0.0124 (16)	0.0168 (15)	0.0043 (13)	−0.0014 (13)
C6	0.048 (2)	0.0265 (19)	0.0164 (17)	0.0088 (18)	0.0051 (16)	−0.0063 (15)
C7	0.041 (2)	0.0232 (19)	0.0169 (17)	0.0077 (17)	0.0060 (15)	−0.0027 (14)
C8	0.0332 (19)	0.0274 (19)	0.0143 (16)	0.0155 (16)	0.0045 (14)	0.0022 (13)
C9	0.066 (3)	0.024 (2)	0.0220 (19)	0.014 (2)	0.004 (2)	−0.0040 (16)
C10	0.049 (2)	0.028 (2)	0.0202 (19)	0.0114 (19)	0.0094 (17)	0.0039 (15)
C11	0.0295 (19)	0.0256 (18)	0.0158 (16)	0.0118 (16)	0.0035 (14)	0.0015 (14)
O1	0.0471 (17)	0.0382 (17)	0.0201 (14)	0.0155 (14)	0.0028 (12)	−0.0103 (12)
O2	0.0280 (13)	0.0335 (14)	0.0146 (12)	0.0141 (12)	0.0031 (10)	−0.0006 (10)
O3	0.0389 (16)	0.0338 (15)	0.0338 (15)	0.0194 (13)	−0.0063 (13)	−0.0001 (12)
O4	0.0457 (17)	0.0376 (16)	0.0345 (15)	0.0230 (14)	−0.0144 (13)	−0.0074 (12)
O5	0.059 (2)	0.041 (2)	0.077 (3)	0.0188 (18)	−0.026 (2)	−0.0295 (18)

Geometric parameters (Å, º)

Eu1—O1^i	2.312 (3)	N3—O4	1.270 (4)
Eu1—O1^ii	2.312 (3)	N3—O3	1.277 (4)
Eu1—O1	2.312 (3)	C1—O1	1.256 (4)
Eu1—O4^i	2.469 (3)	C1—O2	1.261 (5)
Eu1—O4^ii	2.469 (3)	C1—C2	1.488 (5)
Eu1—O4	2.469 (3)	C2—C3	1.386 (5)
Eu1—O3	2.518 (3)	C2—C7	1.390 (5)
Eu1—O3^ii	2.518 (3)	C3—C4	1.384 (5)
Eu1—O3^i	2.518 (3)	C3—H3A	0.9300
Eu1—N3^i	2.927 (3)	C4—C5	1.380 (5)
Eu1—N3	2.927 (3)	C4—H4A	0.9300
Eu1—N3^ii	2.927 (3)	C5—C6	1.388 (5)
Cu1—O2^iii	1.945 (2)	C5—C8	1.486 (4)
Cu1—O2^iv	1.945 (2)	C6—C7	1.389 (5)
Cu1—N1	2.035 (3)	C6—H6A	0.9300
Cu1—N1^v	2.035 (3)	C7—H7A	0.9300
Cu1—O3^vi	2.580 (3)	C8—C11	1.380 (5)
Cu1—O3^vii	2.580 (3)	C8—C9	1.384 (5)
N1—C11	1.334 (4)	C9—H9A	0.9300
N1—C10	1.343 (5)	C10—H10A	0.9300
N2—C10	1.319 (5)	C11—H11A	0.9300
N2—C9	1.330 (5)	O2—Cu1^viii	1.945 (2)
N3—O5	1.208 (4)
O1^i—Eu1—O1^ii	85.90 (11)	N3^i—Eu1—N3^ii	97.68 (9)
O1^i—Eu1—O1	85.90 (11)	N3—Eu1—N3^ii	97.68 (9)
O1^ii—Eu1—O1	85.90 (11)	O2^iii—Cu1—O2^iv	96.56 (15)
O1^i—Eu1—O4^i	146.86 (10)	O2^iii—Cu1—N1	166.84 (11)
O1^ii—Eu1—O4^i	124.99 (9)	O2^iv—Cu1—N1	88.14 (11)
O1—Eu1—O4^i	84.92 (10)	O2^iii—Cu1—N1^v	88.14 (11)
O1^i—Eu1—O4^ii	84.92 (10)	O2^iv—Cu1—N1^v	166.84 (11)
O1^ii—Eu1—O4^ii	146.86 (10)	N1—Cu1—N1^v	89.98 (16)
O1—Eu1—O4^ii	124.99 (9)	O2^iii—Cu1—O3^vi	100.65 (10)
O4^i—Eu1—O4^ii	74.64 (11)	O2^iv—Cu1—O3^vi	82.50 (10)
O1^i—Eu1—O4	125.00 (9)	N1—Cu1—O3^vi	92.13 (10)
O1^ii—Eu1—O4	84.92 (11)	N1^v—Cu1—O3^vi	84.56 (10)
O1—Eu1—O4	146.86 (10)	O2^iii—Cu1—O3^vii	82.50 (10)
O4^i—Eu1—O4	74.64 (11)	O2^iv—Cu1—O3^vii	100.65 (10)
O4^ii—Eu1—O4	74.64 (11)	N1—Cu1—O3^vii	84.56 (10)
O1^i—Eu1—O3	74.13 (9)	N1^v—Cu1—O3^vii	92.13 (10)
O1^ii—Eu1—O3	74.35 (10)	O3^vi—Cu1—O3^vii	175.33 (13)
O1—Eu1—O3	152.61 (10)	C11—N1—C10	116.7 (3)
O4^i—Eu1—O3	121.91 (10)	C11—N1—Cu1	121.3 (2)
O4^ii—Eu1—O3	72.51 (9)	C10—N1—Cu1	122.0 (2)
O4—Eu1—O3	51.18 (9)	C10—N2—C9	116.2 (3)
O1^i—Eu1—O3^ii	74.35 (10)	O5—N3—O4	122.8 (4)
O1^ii—Eu1—O3^ii	152.62 (10)	O5—N3—O3	121.6 (4)
O1—Eu1—O3^ii	74.13 (9)	O4—N3—O3	115.6 (3)
O4^i—Eu1—O3^ii	72.51 (9)	O5—N3—Eu1	177.8 (3)
O4^ii—Eu1—O3^ii	51.18 (9)	O4—N3—Eu1	56.68 (17)
O4—Eu1—O3^ii	121.90 (10)	O3—N3—Eu1	58.92 (18)
O3—Eu1—O3^ii	116.62 (4)	O1—C1—O2	124.3 (3)
O1^i—Eu1—O3^i	152.62 (10)	O1—C1—C2	118.4 (3)
O1^ii—Eu1—O3^i	74.13 (9)	O2—C1—C2	117.2 (3)
O1—Eu1—O3^i	74.35 (10)	C3—C2—C7	118.5 (3)
O4^i—Eu1—O3^i	51.18 (9)	C3—C2—C1	120.0 (3)
O4^ii—Eu1—O3^i	121.91 (10)	C7—C2—C1	121.2 (3)
O4—Eu1—O3^i	72.51 (9)	C4—C3—C2	120.9 (3)
O3—Eu1—O3^i	116.62 (4)	C4—C3—H3A	119.5
O3^ii—Eu1—O3^i	116.61 (4)	C2—C3—H3A	119.5
O1^i—Eu1—N3^i	162.42 (10)	C5—C4—C3	120.9 (3)
O1^ii—Eu1—N3^i	99.78 (10)	C5—C4—H4A	119.6
O1—Eu1—N3^i	78.00 (11)	C3—C4—H4A	119.6
O4^i—Eu1—N3^i	25.45 (9)	C4—C5—C6	118.4 (3)
O4^ii—Eu1—N3^i	98.49 (10)	C4—C5—C8	121.3 (3)
O4—Eu1—N3^i	72.33 (9)	C6—C5—C8	120.2 (3)
O3—Eu1—N3^i	123.38 (9)	C5—C6—C7	121.0 (3)
O3^ii—Eu1—N3^i	94.27 (10)	C5—C6—H6A	119.5
O3^i—Eu1—N3^i	25.74 (9)	C7—C6—H6A	119.5
O1^i—Eu1—N3	99.78 (10)	C6—C7—C2	120.2 (3)
O1^ii—Eu1—N3	78.00 (11)	C6—C7—H7A	119.9
O1—Eu1—N3	162.42 (10)	C2—C7—H7A	119.9
O4^i—Eu1—N3	98.49 (10)	C11—C8—C9	114.6 (3)
O4^ii—Eu1—N3	72.33 (9)	C11—C8—C5	122.7 (3)
O4—Eu1—N3	25.45 (9)	C9—C8—C5	122.6 (3)
O3—Eu1—N3	25.74 (9)	N2—C9—C8	124.1 (4)
O3^ii—Eu1—N3	123.38 (9)	N2—C9—H9A	118.0
O3^i—Eu1—N3	94.27 (10)	C8—C9—H9A	118.0
N3^i—Eu1—N3	97.68 (9)	N2—C10—N1	125.4 (4)
O1^i—Eu1—N3^ii	77.99 (11)	N2—C10—H10A	117.3
O1^ii—Eu1—N3^ii	162.42 (10)	N1—C10—H10A	117.3
O1—Eu1—N3^ii	99.78 (10)	N1—C11—C8	123.0 (3)
O4^i—Eu1—N3^ii	72.33 (9)	N1—C11—H11A	118.5
O4^ii—Eu1—N3^ii	25.45 (9)	C8—C11—H11A	118.5
O4—Eu1—N3^ii	98.49 (10)	C1—O1—Eu1	164.0 (3)
O3—Eu1—N3^ii	94.28 (10)	C1—O2—Cu1^viii	128.1 (2)
O3^ii—Eu1—N3^ii	25.74 (9)	N3—O3—Eu1	95.3 (2)
O3^i—Eu1—N3^ii	123.38 (9)	N3—O4—Eu1	97.9 (2)

Symmetry codes: (i) −x+y+2, −x+1, z; (ii) −y+1, x−y−1, z; (iii) −y+4/3, −x+5/3, z+1/6; (iv) y+2/3, −x+y+4/3, −z+1/3; (v) −x+2, −x+y+1, −z+1/2; (vi) −x+y+7/3, y+2/3, z+1/6; (vii) x−y−1/3, x−2/3, −z+1/3; (viii) x−y+2/3, x−2/3, −z+1/3.