A new hexa­molybdate-based copper–2,2′-bi­imidazole coordination polymer serving as an acid catalyst and support for enzyme immobilization

The hydro­thermal reaction of (NH₄)₃[CoMo₆O₂₄H₆]·7H₂O (CoMo₆), CuCl₂·2H₂O and 2,2′-bi­imidazole (H₂biim) led to the formation of a new coordination polymer, namely poly[di­aqua­bis­(2,2′-bi­imidazole)­hexa-μ₃-oxo-octa-μ₂-oxo-hexa­oxodicopper(II)hexa­molybdate(VI)], [Cu₂Mo₆O₂₀(C₆H₆N₄)₂(H₂O)₂]_n (Cu-Mo₆O₂₀), at pH 2–3. It is obvious that in the formation of crystalline Cu-Mo₆O₂₀, the original Anderson-type skeleton of heteropolymolybdate CoMo₆ was broken and the new isopolyhexa­molybdate Mo₆O₂₀ unit was assembled. In Cu-Mo₆O₂₀, one Mo₆O₂₀ unit connects four [Cu(H₂biim)(H₂O)]²⁺ ions in a penta­coordinate mode via four terminal O atoms, resulting in a tetra-supported structure, and each Cu^II ion is shared by two adjacent Mo₆O₂₀ units. Infinite one-dimensional chains are established by linkage between two adjacent Mo₆O₂₀ units and two Cu^II ions, and these chains are further packed into a three-dimensional framework by hydrogen bonds, π–π inter­actions and electrostatic attractions. The catalytic performance of this crystalline material used as an efficient and reusable heterogeneous acid catalyst for carbonyl-group protection is discussed. In addition, Cu-Mo₆O₂₀ was applied as a new support for enzyme (horseradish peroxidase, HRP) immobilization, forming immobilized enzyme HRP/Cu-Mo₆O₂₀. HRP/Cu-Mo₆O₂₀ showed good catalytic activity and could be reused.

Computing details

Data collection: SMART (Bruker, 2005); cell refinement: SMART (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

(I)

Crystal data

[Cu2Mo6O20(C6H6N4)2(H2O)2]	Z = 1
Mr = 1327.07	F(000) = 630
Triclinic, P1	Dx = 2.904 Mg m^−3
a = 8.065 (3) Å	Mo Kα radiation, λ = 0.71073 Å
b = 10.293 (4) Å	Cell parameters from 2954 reflections
c = 10.837 (4) Å	θ = 2.1–31.0°
α = 64.090 (5)°	µ = 3.87 mm^−1
β = 75.186 (5)°	T = 296 K
γ = 71.141 (5)°	Block, green
V = 758.8 (5) Å^3	0.09 × 0.07 × 0.06 mm

Data collection

Bruker SMART CCD area detector diffractometer	2409 reflections with I > 2σ(I)
phi and ω scans	Rint = 0.011
Absorption correction: multi-scan (SADABS; Sheldrick, 2003)	θmax = 25.0°, θmin = 2.1°
Tmin = 0.724, Tmax = 0.795	h = −9→9
3875 measured reflections	k = −12→5
2639 independent reflections	l = −12→11

Refinement

Refinement on F^2	Hydrogen site location: mixed
Least-squares matrix: full	H atoms treated by a mixture of independent and constrained refinement
R[F^2 > 2σ(F^2)] = 0.018	w = 1/[σ^2(Fo^2) + (0.0182P)^2 + 0.8925P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.042	(Δ/σ)max = 0.002
S = 1.06	Δρmax = 0.36 e Å^−3
2639 reflections	Δρmin = −0.49 e Å^−3
235 parameters	Extinction correction: SHELXL2014 (Sheldrick, 2015), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
2 restraints	Extinction coefficient: 0.00089 (19)

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
Mo1	0.98397 (3)	0.33719 (3)	0.03177 (3)	0.01070 (8)
Mo2	0.60552 (3)	0.61615 (3)	−0.14598 (3)	0.01038 (8)
Mo3	1.36521 (3)	0.35113 (3)	−0.13694 (3)	0.01252 (8)
Cu1	0.74909 (5)	0.03949 (4)	0.26078 (4)	0.01640 (10)
O1	0.8072 (3)	0.3884 (2)	−0.0564 (2)	0.0153 (5)
O2	0.4604 (3)	0.4673 (2)	−0.0845 (2)	0.0130 (5)
O3	0.4304 (3)	0.7745 (2)	−0.1873 (2)	0.0171 (5)
O4	1.1704 (3)	0.2611 (2)	−0.0937 (2)	0.0160 (5)
O5	0.7053 (3)	0.6093 (3)	−0.3023 (2)	0.0205 (5)
O6	1.2507 (3)	0.3138 (2)	0.0931 (2)	0.0139 (5)
O7	1.5341 (3)	0.1920 (3)	−0.1027 (2)	0.0221 (5)
O8	0.9664 (3)	0.1694 (2)	0.1693 (2)	0.0179 (5)
O9	0.9035 (3)	0.4712 (2)	0.1197 (2)	0.0137 (5)
O10	1.3870 (3)	0.4373 (3)	−0.3123 (2)	0.0261 (6)
N1	0.9166 (4)	−0.1542 (3)	0.3601 (3)	0.0219 (6)
N2	0.7007 (4)	0.0549 (3)	0.4419 (3)	0.0208 (6)
N3	1.0422 (4)	−0.2950 (3)	0.5499 (3)	0.0255 (7)
H3B	1.0674	−0.3268	0.6323	0.031*
N4	0.7703 (4)	−0.0341 (4)	0.6520 (3)	0.0277 (7)
H4B	0.8209	−0.0913	0.7249	0.033*
C1	0.9213 (4)	−0.1711 (4)	0.4888 (3)	0.0193 (7)
C2	0.8025 (4)	−0.0553 (4)	0.5341 (3)	0.0188 (7)
C3	1.0407 (5)	−0.2745 (4)	0.3394 (4)	0.0294 (9)
H3A	1.0670	−0.2928	0.2589	0.035*
C4	1.1183 (5)	−0.3617 (4)	0.4566 (4)	0.0315 (9)
H4A	1.2061	−0.4497	0.4707	0.038*
C5	0.5996 (5)	0.1512 (4)	0.5058 (4)	0.0259 (8)
H5A	0.5169	0.2391	0.4661	0.031*
C6	0.6412 (5)	0.0962 (4)	0.6357 (4)	0.0306 (9)
H6A	0.5920	0.1384	0.7013	0.037*
O1W	0.7698 (4)	0.0086 (3)	0.0923 (3)	0.0286 (6)
H1WA	0.795 (5)	−0.076 (2)	0.088 (4)	0.031 (11)*
H1WB	0.689 (4)	0.066 (4)	0.042 (4)	0.034 (12)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Mo1	0.00964 (14)	0.00824 (14)	0.01472 (15)	−0.00114 (10)	−0.00385 (10)	−0.00442 (11)
Mo2	0.01055 (14)	0.00962 (14)	0.01067 (14)	−0.00216 (10)	−0.00322 (10)	−0.00288 (11)
Mo3	0.01202 (14)	0.01383 (15)	0.01426 (15)	−0.00256 (11)	−0.00265 (11)	−0.00763 (12)
Cu1	0.0205 (2)	0.0121 (2)	0.0155 (2)	0.00063 (17)	−0.00799 (17)	−0.00461 (17)
O1	0.0134 (11)	0.0148 (11)	0.0190 (12)	−0.0011 (9)	−0.0050 (9)	−0.0080 (10)
O2	0.0120 (11)	0.0151 (11)	0.0124 (11)	−0.0038 (9)	−0.0036 (9)	−0.0044 (10)
O3	0.0161 (12)	0.0150 (12)	0.0188 (12)	−0.0014 (10)	−0.0062 (9)	−0.0050 (10)
O4	0.0148 (11)	0.0154 (12)	0.0234 (12)	−0.0027 (9)	−0.0029 (9)	−0.0131 (10)
O5	0.0213 (12)	0.0219 (13)	0.0172 (12)	−0.0053 (10)	−0.0009 (10)	−0.0076 (11)
O6	0.0132 (11)	0.0125 (11)	0.0166 (12)	−0.0017 (9)	−0.0049 (9)	−0.0057 (9)
O7	0.0199 (13)	0.0208 (13)	0.0283 (14)	0.0009 (10)	−0.0068 (10)	−0.0142 (11)
O8	0.0186 (12)	0.0111 (11)	0.0219 (12)	−0.0046 (9)	−0.0082 (10)	−0.0009 (10)
O9	0.0130 (11)	0.0122 (11)	0.0171 (12)	−0.0028 (9)	−0.0030 (9)	−0.0065 (10)
O10	0.0269 (14)	0.0349 (15)	0.0168 (12)	−0.0090 (12)	−0.0044 (10)	−0.0083 (11)
N1	0.0239 (15)	0.0169 (15)	0.0223 (16)	−0.0009 (13)	−0.0073 (13)	−0.0060 (13)
N2	0.0228 (15)	0.0196 (15)	0.0163 (15)	−0.0003 (12)	−0.0074 (12)	−0.0047 (13)
N3	0.0262 (16)	0.0206 (16)	0.0250 (17)	0.0009 (13)	−0.0148 (13)	−0.0031 (14)
N4	0.0320 (17)	0.0306 (18)	0.0149 (15)	−0.0002 (14)	−0.0101 (13)	−0.0053 (14)
C1	0.0201 (17)	0.0138 (17)	0.0188 (18)	−0.0036 (14)	−0.0069 (14)	0.0003 (14)
C2	0.0202 (17)	0.0172 (17)	0.0161 (17)	−0.0065 (14)	−0.0040 (14)	−0.0017 (14)
C3	0.033 (2)	0.021 (2)	0.034 (2)	0.0026 (17)	−0.0087 (17)	−0.0151 (18)
C4	0.029 (2)	0.022 (2)	0.041 (2)	0.0066 (16)	−0.0157 (18)	−0.0123 (19)
C5	0.028 (2)	0.0219 (19)	0.0231 (19)	0.0049 (16)	−0.0083 (16)	−0.0095 (16)
C6	0.034 (2)	0.034 (2)	0.025 (2)	−0.0009 (18)	−0.0041 (17)	−0.0181 (18)
O1W	0.0431 (17)	0.0167 (14)	0.0300 (15)	0.0070 (12)	−0.0196 (13)	−0.0145 (12)

Geometric parameters (Å, º)

Mo1—O1	1.730 (2)	Cu1—O8	2.305 (2)
Mo1—O8	1.739 (2)	O2—Mo3^iv	1.938 (2)
Mo1—O9	1.868 (2)	O2—Mo2^ii	2.236 (2)
Mo1—O4	1.961 (2)	O3—Cu1^ii	1.965 (2)
Mo1—O9^i	2.230 (2)	O6—Mo2^i	1.853 (2)
Mo1—O6	2.320 (2)	O9—Mo1^i	2.230 (2)
Mo1—Mo3	3.1621 (11)	O9—Mo3^i	2.367 (2)
Mo1—Mo1^i	3.1980 (14)	N1—C1	1.337 (4)
Mo2—O5	1.701 (2)	N1—C3	1.383 (5)
Mo2—O3	1.746 (2)	N2—C2	1.336 (4)
Mo2—O6^i	1.853 (2)	N2—C5	1.384 (4)
Mo2—O2	2.007 (2)	N3—C1	1.344 (4)
Mo2—O2^ii	2.236 (2)	N3—C4	1.374 (5)
Mo2—O1	2.332 (2)	N3—H3B	0.8600
Mo2—Mo3^i	3.3005 (12)	N4—C2	1.337 (5)
Mo3—O10	1.699 (2)	N4—C6	1.378 (5)
Mo3—O7	1.720 (2)	N4—H4B	0.8600
Mo3—O4	1.932 (2)	C1—C2	1.453 (5)
Mo3—O2^iii	1.938 (2)	C3—C4	1.362 (5)
Mo3—O6	2.330 (2)	C3—H3A	0.9300
Mo3—O9^i	2.367 (2)	C4—H4A	0.9300
Mo3—Mo2^i	3.3005 (12)	C5—C6	1.356 (5)
Cu1—O1W	1.944 (3)	C5—H5A	0.9300
Cu1—O3^ii	1.965 (2)	C6—H6A	0.9300
Cu1—N2	1.968 (3)	O1W—H1WA	0.848 (10)
Cu1—N1	2.021 (3)	O1W—H1WB	0.847 (10)
O1—Mo1—O8	105.53 (10)	O2^iii—Mo3—Mo1	107.91 (7)
O1—Mo1—O9	99.82 (10)	O6—Mo3—Mo1	47.03 (5)
O8—Mo1—O9	101.97 (11)	O9^i—Mo3—Mo1	44.76 (6)
O1—Mo1—O4	98.42 (10)	O10—Mo3—Mo2^i	142.83 (9)
O8—Mo1—O4	99.33 (10)	O7—Mo3—Mo2^i	91.19 (8)
O9—Mo1—O4	146.97 (9)	O4—Mo3—Mo2^i	107.00 (7)
O1—Mo1—O9^i	93.92 (9)	O2^iii—Mo3—Mo2^i	41.02 (6)
O8—Mo1—O9^i	160.21 (9)	O6—Mo3—Mo2^i	33.08 (5)
O9—Mo1—O9^i	77.76 (10)	O9^i—Mo3—Mo2^i	79.92 (5)
O4—Mo1—O9^i	73.73 (9)	Mo1—Mo3—Mo2^i	77.48 (2)
O1—Mo1—O6	164.31 (9)	O1W—Cu1—O3^ii	88.80 (10)
O8—Mo1—O6	89.31 (9)	O1W—Cu1—N2	171.61 (13)
O9—Mo1—O6	81.63 (8)	O3^ii—Cu1—N2	91.04 (10)
O4—Mo1—O6	73.66 (8)	O1W—Cu1—N1	97.25 (11)
O9^i—Mo1—O6	71.01 (8)	O3^ii—Cu1—N1	172.79 (11)
O1—Mo1—Mo3	119.19 (8)	N2—Cu1—N1	82.40 (12)
O8—Mo1—Mo3	116.11 (8)	O1W—Cu1—O8	92.83 (11)
O9—Mo1—Mo3	111.74 (7)	O3^ii—Cu1—O8	90.16 (9)
O4—Mo1—Mo3	35.38 (6)	N2—Cu1—O8	95.57 (11)
O9^i—Mo1—Mo3	48.38 (5)	N1—Cu1—O8	93.43 (11)
O6—Mo1—Mo3	47.29 (6)	Mo1—O1—Mo2	131.51 (11)
O1—Mo1—Mo1^i	98.47 (7)	Mo3^iv—O2—Mo2	146.84 (12)
O8—Mo1—Mo1^i	141.00 (8)	Mo3^iv—O2—Mo2^ii	104.30 (9)
O9—Mo1—Mo1^i	42.95 (7)	Mo2—O2—Mo2^ii	108.61 (9)
O4—Mo1—Mo1^i	107.11 (7)	Mo2—O3—Cu1^ii	171.89 (14)
O9^i—Mo1—Mo1^i	34.80 (6)	Mo3—O4—Mo1	108.63 (10)
O6—Mo1—Mo1^i	71.83 (5)	Mo2^i—O6—Mo1	151.38 (11)
Mo3—Mo1—Mo1^i	75.714 (13)	Mo2^i—O6—Mo3	103.60 (10)
O5—Mo2—O3	103.81 (11)	Mo1—O6—Mo3	85.69 (7)
O5—Mo2—O6^i	105.88 (11)	Mo1—O8—Cu1	133.36 (11)
O3—Mo2—O6^i	99.09 (10)	Mo1—O9—Mo1^i	102.24 (10)
O5—Mo2—O2	99.76 (10)	Mo1—O9—Mo3^i	133.99 (10)
O3—Mo2—O2	96.41 (10)	Mo1^i—O9—Mo3^i	86.86 (8)
O6^i—Mo2—O2	145.72 (9)	C1—N1—C3	106.1 (3)
O5—Mo2—O2^ii	157.22 (10)	C1—N1—Cu1	111.6 (2)
O3—Mo2—O2^ii	98.12 (9)	C3—N1—Cu1	142.1 (3)
O6^i—Mo2—O2^ii	76.26 (9)	C2—N2—C5	106.2 (3)
O2—Mo2—O2^ii	71.39 (9)	C2—N2—Cu1	113.6 (2)
O5—Mo2—O1	84.46 (10)	C5—N2—Cu1	140.0 (2)
O3—Mo2—O1	170.22 (9)	C1—N3—C4	107.4 (3)
O6^i—Mo2—O1	83.37 (9)	C1—N3—H3B	126.3
O2—Mo2—O1	76.79 (8)	C4—N3—H3B	126.3
O2^ii—Mo2—O1	73.17 (8)	C2—N4—C6	107.6 (3)
O5—Mo2—Mo3^i	147.98 (8)	C2—N4—H4B	126.2
O3—Mo2—Mo3^i	92.04 (7)	C6—N4—H4B	126.2
O6^i—Mo2—Mo3^i	43.33 (7)	N1—C1—N3	110.8 (3)
O2—Mo2—Mo3^i	105.98 (6)	N1—C1—C2	116.3 (3)
O2^ii—Mo2—Mo3^i	34.67 (6)	N3—C1—C2	132.8 (3)
O1—Mo2—Mo3^i	83.25 (6)	N2—C2—N4	110.7 (3)
O10—Mo3—O7	105.13 (12)	N2—C2—C1	115.8 (3)
O10—Mo3—O4	103.31 (11)	N4—C2—C1	133.5 (3)
O7—Mo3—O4	98.59 (11)	C4—C3—N1	108.7 (3)
O10—Mo3—O2^iii	102.58 (11)	C4—C3—H3A	125.7
O7—Mo3—O2^iii	99.05 (10)	N1—C3—H3A	125.7
O4—Mo3—O2^iii	143.45 (9)	C3—C4—N3	107.0 (3)
O10—Mo3—O6	158.41 (10)	C3—C4—H4A	126.5
O7—Mo3—O6	96.44 (10)	N3—C4—H4A	126.5
O4—Mo3—O6	73.93 (8)	C6—C5—N2	108.7 (3)
O2^iii—Mo3—O6	72.48 (8)	C6—C5—H5A	125.7
O10—Mo3—O9^i	90.22 (10)	N2—C5—H5A	125.7
O7—Mo3—O9^i	163.34 (10)	C5—C6—N4	106.9 (3)
O4—Mo3—O9^i	71.06 (9)	C5—C6—H6A	126.6
O2^iii—Mo3—O9^i	83.52 (8)	N4—C6—H6A	126.6
O6—Mo3—O9^i	68.49 (7)	Cu1—O1W—H1WA	125 (3)
O10—Mo3—Mo1	119.29 (8)	Cu1—O1W—H1WB	115 (3)
O7—Mo3—Mo1	119.71 (9)	H1WA—O1W—H1WB	108 (4)
O4—Mo3—Mo1	36.00 (6)
O8—Mo1—O1—Mo2	135.03 (15)	Mo1^i—Mo1—O9—Mo3^i	97.56 (16)
O9—Mo1—O1—Mo2	29.57 (16)	C3—N1—C1—N3	0.3 (4)
O4—Mo1—O1—Mo2	−122.78 (15)	Cu1—N1—C1—N3	−175.7 (2)
O9^i—Mo1—O1—Mo2	−48.67 (15)	C3—N1—C1—C2	179.0 (3)
O6—Mo1—O1—Mo2	−64.4 (4)	Cu1—N1—C1—C2	3.1 (4)
Mo3—Mo1—O1—Mo2	−92.25 (14)	C4—N3—C1—N1	−0.4 (4)
Mo1^i—Mo1—O1—Mo2	−13.94 (15)	C4—N3—C1—C2	−178.9 (4)
O1—Mo1—O8—Cu1	−10.07 (19)	C5—N2—C2—N4	0.4 (4)
O9—Mo1—O8—Cu1	93.81 (16)	Cu1—N2—C2—N4	176.5 (2)
O4—Mo1—O8—Cu1	−111.59 (16)	C5—N2—C2—C1	180.0 (3)
O9^i—Mo1—O8—Cu1	−179.13 (17)	Cu1—N2—C2—C1	−3.9 (4)
O6—Mo1—O8—Cu1	175.10 (16)	C6—N4—C2—N2	0.0 (4)
Mo3—Mo1—O8—Cu1	−144.49 (12)	C6—N4—C2—C1	−179.5 (4)
Mo1^i—Mo1—O8—Cu1	115.81 (14)	N1—C1—C2—N2	0.5 (5)
O1—Mo1—O9—Mo1^i	−91.91 (10)	N3—C1—C2—N2	178.9 (4)
O8—Mo1—O9—Mo1^i	159.76 (9)	N1—C1—C2—N4	179.9 (4)
O4—Mo1—O9—Mo1^i	30.7 (2)	N3—C1—C2—N4	−1.7 (7)
O9^i—Mo1—O9—Mo1^i	−0.001 (1)	C1—N1—C3—C4	−0.1 (4)
O6—Mo1—O9—Mo1^i	72.26 (9)	Cu1—N1—C3—C4	173.8 (3)
Mo3—Mo1—O9—Mo1^i	35.09 (9)	N1—C3—C4—N3	−0.1 (5)
O1—Mo1—O9—Mo3^i	5.65 (17)	C1—N3—C4—C3	0.3 (4)
O8—Mo1—O9—Mo3^i	−102.68 (15)	C2—N2—C5—C6	−0.7 (4)
O4—Mo1—O9—Mo3^i	128.26 (16)	Cu1—N2—C5—C6	−175.1 (3)
O9^i—Mo1—O9—Mo3^i	97.56 (16)	N2—C5—C6—N4	0.7 (5)
O6—Mo1—O9—Mo3^i	169.82 (16)	C2—N4—C6—C5	−0.4 (4)
Mo3—Mo1—O9—Mo3^i	132.65 (12)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N3—H3B···O9^v	0.86	2.47	3.303 (4)	164
N4—H4B···O8^v	0.86	2.05	2.834 (4)	151
N4—H4B···O6^v	0.86	2.41	3.013 (4)	128
O1W—H1WA···O4^vi	0.85 (1)	1.81 (1)	2.654 (3)	174 (4)
O1W—H1WB···O7^iv	0.85 (1)	1.97 (1)	2.809 (3)	170 (4)

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