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Article

Mechanochemical Access to Elusive Metal Diphosphinate Coordination Polymer

1
Consiglio Nazionale delle Ricerche—Istituto di Chimica dei Composti OrganoMetallici (CNR-ICCOM) Via Madonna del Piano 10, Sesto Fiorentino, I-50019 Firenze, Italy
2
Dipartimento di Chimica “Ugo Schiff”, University of Florence, Via della Lastruccia 3, Sesto Fiorentino, I-50019 Firenze, Italy
3
Dipartimento di Chimica, Biologia e Biotecnologie, University of Perugia, Via Elce di Sotto 8, I-06123 Perugia, Italy
*
Author to whom correspondence should be addressed.
Crystals 2019, 9(6), 283; https://doi.org/10.3390/cryst9060283
Submission received: 24 April 2019 / Revised: 21 May 2019 / Accepted: 25 May 2019 / Published: 29 May 2019
(This article belongs to the Special Issue Metal Phosphonates and Phosphinates)

Abstract

:
Several binary metal diphosphinate compounds (ML) have been reported for diphosphinate bonded by a single methylene fragment. In case of longer bridges, binary products are difficult to isolate in crystalline form. Here, using a solvent assisted mechano-chemistry synthesis, we report two new ML crystalline phases, one hydrated and one anhydrous. The hydrated phase is a 2D coordination polymer with an open framework structure. Its network displays a new topology for coordination polymers and metal organic frameworks. The thermal behavior of the two phases has been studied. Finally, the importance of the bridge length is discussed in view of known metal diphosphinate compounds.

Graphical Abstract

1. Introduction

For diphosphinates connected by a long bridge, a trio is better than a duet. We recall that phosphinates are a class of ligands widely studied in the 1960s and 1970s of the twentieth century to build inorganic polymers [1]. Nowadays, after a few decades of forgetfulness, a new use has been found for phosphinates as flame retardants, by replacing brominate polymers banned by the European Community [2]. In the last few years, phospinates have also been used as novel ligands for the synthesis of robust Metal-organic Frameworks (MOF). For instance, in 2018 Demel and co-workers used phenylene-1,4-bis(methylphosphinic acid) (PBPA) for the synthesis of porous iron(II) MOF [3]. In this study, we focus on a particular class of phosphinates, namely those with two phosphinate groups connected by an organic bridge. In the last 10 years, we have extensively studied P,P′-diphenylmethylene diphosphinic acid (H2pcp), P,P′-diphenylethylene diphosphinic acid (H2pc2p) and P,P′-diphenyl-p-xylylene diphosphinic acid (H2pxylp) [4,5] as shown in Scheme 1. Different diphosphinic acids were also reported [6,7].
In particular, the coordination ability of pcp towards alkaline earth metals [8,9,10], bivalent cations such tin [11] and lead [12] as well as several transition metal ions [11,13,14,15,16,17] are previously reported. Depending on the metal and the use of ancillary ligands, mono- [14,18] and multinuclear complexes [19,20], 1D [21,22,23] or 2D [21,23] coordination polymers were obtained. The isolation of two isoreticular metal organic nano tubes (MONT) built by using copper(II) metal ion, pcp and two types of bi-pyridine was one of our most interesting results [24,25], also due to the different behavior of the two materials in water. [21] On the other hand, pc2p and pxylp ligands were found to form 2D and 3D coordination polymers easily [26,27,28]. One of the latter, features porous channels able to reversibly adsorb methanol [26]. Under heating, different pseudo polymorph coordination polymers have been obtained upon removal of the coordinated water molecules [26,27,28].
We have already discussed the different coordination ability of pcp with respect to the other diphosphinate ligands with longer bridges [20]. From the reported structures, while pcp prefers to chelate the metal atoms, the other ligands connect different metal ions with their phosphinate units [26,27,28] and only when a co-ligand such as 2,2′-bipy leaves free, only the cis positions pc2p is found to chelate a metal center [20]. We also noticed that binary metal pcp compounds are easily obtained, while the corresponding pc2p systems are elusive, as the common synthetic routes employed (solution or hydrothermal methods) are not satisfactory. For instance, in the case of Ni, pc2p, bipy systems, we obtained cationic 1D chains of [Ni(H2O)4(bipy)]n2+ and dianionic diphosphinate moieties not bonding to the metal center [28].
In this work, for the first time, we were able to isolate metal pc2p coordination polymers, using Cu(II) as metal atom using a liquid assisted mechanochemical synthesis [29]. Depending on the amount of water used, a hydrous phase of formula [[Cu4(pc2p)4(H2O)6]·8(H2O)]n, 1, and Cu(pc2p) anhydrous phase, 2, were obtained. The X-ray analysis of 1 revealed a two-dimensional network with a potential porous structure, a unique characteristic in the family of the metal diphosphinate series. Topological analysis [30] was also carried out and it revealed a new topology type for 2 in the field of MOF and coordination polymers. In water 1 and 2 did not interconvert as shown by the thermal behavior of 1 and 2 studied by TGA and Temperature Dependent Powder Diffraction experiment (TDXD).

2. Materials and Methods

All reagents were analytical-grade commercial products and were used without further purification. The H2pc2p were prepared as previously described [31]. Elemental analyses (C, H, N) were performed with an EA 1108 CHNS-O automatic analyzer (Carlo Erba Instruments, Milan, Italy ). XRD data was collected on a X’Pert PRO diffractometer (Panalytical, Almelo, the Netherlands) with Cu Kα radiation (λ = 1.5418 Å). Thermodiffractometric analysis were performed under air with an Anton Paar HTK 1200N hot chamber (Anton Paar, Graz, Austria). Thermogravimetric analyses (TGA) were performed on an EXSTAR Seiko 6200 analyzer (Seiko Instruments, Tokyo, Japan) under air (100 mL/min) at a heating rate of 10°C/min. The P/Cu ratio in 1 and 2 was measured using the X-ray (EDS) microanalysis system, Octane Elect Super Team Basic, (EDAX, AMETEK, Mahwah, NJ, USA) of a Gaia 3 (Tescan s.r.o, Brno, Czech Republic) FIB-SEM (Focused Ion Beam-Scanning Electron Microscope) Electron beam used for SEM imaging.

2.1. Synthesis of [[Cu4(pc2p)4(H2O)6]·8(H2O)]n, 1

In an agate mortar, 1 mL of water was added to Cu acetate monohydrate (42 mg, 0.21 mmol). At the resulting slurry, H2pc2p (65 mg, 0.21 mmol) was added and grounded for 5 minutes. The product was washed with water and dried in air at room temperature. Well-formed blue crystals of 1 were obtained after several days by precipitation from a water solution (20 mL) of Cu acetate monohydrate (42 mg, 0.21 mmol) and H2p2pc (65 mg, 0.21 mmol). For the elemental analysis, the product dried in oven for 2 hours at 120 °C was used. The P/Cu ratio calculated using EDX is between 1.9 and 2.0 either for the dried and the hydrated product. Yield 63 mg, 86%. C28H26Cu2O8P4 (741.50 gmol−1): calcd. C 45.36, H 3.53; found: C 45.27, H 3.59.

2.2. Synthesis of Cupc2p, 2

Cu acetate monohydrate (42 mg, 0.21 mmol) and H2pc2p (65 mg, 0.21 mmol) were ground with two drops of water for 5 minutes in an agate mortar. The product was washed with water and dried in air at room temperature. The P/Cu ratio calculated using EDX is between 1.9 and 2.0. Yield 55 mg, 88%. C28H26Cu2O8P4 (741.50 gmol−1): calcd. C 45.36, H 3.53; found: C 45.28, H 3.65.

2.3. X-Ray Structure Determination

A summary of the crystal data is given in Table 1. An Oxford Diffraction Excalibur 3 diffractometer (Oxford Diffraction Ltd., Abingdon, United Kingdom) equipped with Cu-Kα radiation and CCD area detector was used for data collection at 173K. The software CrysAlis CCD [32], CrysAlis RED [33] and ABSPACK [33] was employed for data collection, data reduction and absorption correction, respectively. Direct methods as coded in Sir97 [34] were used for structure solution. SHELXL program [35] was used for structure refinement on F2 by full-matrix least squares techniques. All non-hydrogen atoms were refined anisotropically. Carbon bonded hydrogen atoms were introduced in calculated positions. The hydrogen atoms of water molecules (except the one bonded to OW5) were found in the Fourier map and refined using distance restraints. CCDC-1910569 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.

3. Results and Discussion

Adding in an agata mortar 0.21 mmol of H2pc2p acid to a slurry of equivalent amount of copper(II) Acetate in 1 mL of water, a phase of formula [[Cu4(pc2p)4(H2O)6]·8(H2O)]n, 1, was obtained. The compound was recognized by the comparison of the X-ray powder diffraction (see Figure S1 in Supplementary Materials) with the calculated pattern of the structure resolved from single crystal grown in solution.
The structure of 1 resulted in a potentially porous open framework 2D coordination polymer and its formula is [[Cu4(pc2p)4(H2O)6]·8(H2O)]n. The asymmetric unit contains two pc2p ligands, three independent copper atoms and nine water molecules, four of them coordinated to copper ions and five as free solvent molecules. Selected distances and angles are reported in Table 2.
Two metal atoms (Cu2 and Cu3) sit on a twofold axis, while the third is in general position. Also, four oxygen atoms of water molecules are on a twofold axis. As illustrated in Figure 1a, the first pc2p ligand is bound to two different Cu1 atoms with O1 and O3 while the other two oxygen atoms are engaged in hydrogen bonds with five different water molecules. All the oxygen atoms of the second pc2p ligand are connected with four different copper ions, namely Cu1, Cu1′, Cu2 and Cu3 (see Figure 1b). Before describing the coordination of copper atoms, it is useful to note that Cu1 metal and pc2p ligands form a two dimensional square grid as shown in Figure 2a.
Figure 1c shows the coordination and the relation between Cu1 and Cu2 metal. Cu1 atom assumes a slightly distorted square pyramidal geometry. The basal positions are occupied by four oxygen atoms of four different pc2p ligands, while the axial position is occupied by a water molecule with a distance Cu1-O20 of 2.4651(14)Å. The latter water is bridging between Cu1 and Cu2. The Cu2 atom is surrounded by three oxygen atoms of three water molecules and by two oxygen atoms of two different pc2p ligands. In this case the geometry around the Cu2 atom is better described as trigonal bi-pyramidal. Finally, three oxygen atoms of three water molecules and two oxygen atoms of two different pc2p ligand are around the Cu3 atom. A sixth water molecules is at 2.8852(6)Å as shown in Figure 1d. Interestingly, the three slightly different copper coordination in 1 is an example of how the Jahn Teller (or pseudo Jahn Teller) effect could influence the metal geometry in five coordinated complexes [36].
The pieces for building the two dimensional network are two square grids of Figure 2a on the ab plane and the strips formed by Cu1, Cu2 and Cu3 metal ions along a axis as shown in Figure 2b. The complete 2D layers are shown in Figure 2c and they have an approximate height of 16Å. The inner part presents rectangular channels of 7.7 × 9.2 Å2 (excluding van der Waals radii) filled with water molecules. Excluding the solvent water molecules, the calculated void volume is 336Å3 and it is more than the 5% of the unit cell volume. The layers are stacked together with the phenyl rings of the pc2p ligands as shown in Figure 3c.
The topological analysis was performed in order to better understand the connections in the 2D network and determine some correlation with known coordination polymers. [30,37,38,39,40] Looking at Figure 1c,d, Cu1 results in a 5-connected node, Cu2 in a 4-connected one, while Cu3 is only 2-connected and it does not contribute to the final topology. Also, the pc2p ligand of P1 and P2 atoms is 2-connected (see Figure 1a). The other pc2p could be considered in two different ways, in one case, in the so called standard representation, by two 3-connected nodes (P3 and P4 atoms) as shown in Figure 3a, in the other, the cluster reduction, the whole pc2p ligand is substituted with a unique single 4-connected node (Figure 3b).
The network, represented in Figure 3a, is a 4 nodal network with two 3, one 4 and one 5 connected vertexes, while the one illustrated in Figure 3b is a 3-nodal net with a 4, 4, 5-connected vertex. The point symbols are {3.5.63.72.83}2{3.5.6}2{32.52.62}{52.8}2 and {3.4.5.66.8} 2{3.42.5.62} 2{32.42.52} respectively. No network with this topology is present to date in the Topcryst topological database [41]. We also decided to not consider the bond between O20 and the Cu1, being longer than a normal Cu-O bond, in order to explore possible connections with other known networks. In this case, the Cu1 is a a 4-connected node, while the Cu2 is reduced to a 2-connected one. Again, the pc2p ligand is considered formed by two 3-connected nodes in the standard representation (Figure 3c) and by a single 4 connected node in the cluster one (Figure 3d). With these choices, the network of Figure 3c is a 3-nodal net with two 3-connected and one 4 connected vertex, known as 3,4L156, while in the other case the 4,4L62 network is obtained as represented in Figure 3d. In the Topcryst database [41] two H-bonded molecular structures for 3,4L156 have been found (CCDC recodes: KEDBUS [42], EJIRIY [43]). Also, one H-bonded structure has the 4,4L62 topology (CCDC refcode ATEYII [44]). To the best of our knowledge, no covalent coordination polymer or MOF shows the same topology as 2.
Using a different synthetic protocol, namely adding ater to a solid mixture of copper(II) Acetate and H2pc2p, a second phase, 2, appeared in the powder X-ray diffraction pattern (see Figure 4d). Eventually, when just a small amount of water was used, pure 2 was synthetized. Compound 2 resulted in an anhydrous phase and it can be written as Cu(pc2p). Unfortunately, due to the poor crystallinity of the product, it was not possible to index the diffraction pattern and we were unable to obtain a single crystal of 2.
The thermal behavior of the two phases was studied by thermogravimetric analysis (TGA) and temperature-dependent X-ray powder diffraction. For 1, in the TGA under nitrogen (Figure 5a) the loss of solvent and coordinated water molecules of 1 is observed below 100 °C (14.5% calcd, 13.8% exp.). Above 200 °C, the degradation of the pc2p ligand begins. The corresponding temperature-dependent X-ray powder diffraction patterns between 25 °C and 120 °C (Figure 5b) show a progressive meaningful shift of the first peak (0,0,2 of phase 1) between 25 °C to 50 °C, indicating a shortening of the c axis. This could be interpreted as the shrinkage of the inorganic layers of 1. In the pattern at 50 °C a new peak at around 5.9° 2θ appeared. At 70 °C, the transformation is complete as shown by the peak at 5.9° 2θ, which is attributable to an anhydrous 1. Evidently, the latter has a different structural arrangement with respect to 2 and the loss of coordinated water results in a collapse of the inorganic layers. Phase 1 does not recover spontaneously at room temperature, but the crystallinity is restored when contacted with water. The TGA of 2 shows that the phase is stable up to 130 °C as shown in Figure 5c without any important weight loss, confirming the anhydrous nature of 2. The temperature-dependent X-ray powder diffraction analysis between 25 °C and 120 °C shows no change in the diffraction pattern (see Figure S2 in Supplementary Materials). The total weight loss up to 800 °C is about 44% which is compatible with the thermal degradation of the organic part which occurs in two different steps (calc. 46.1% with the formula Cupc2p).
Finally using CSD database surveys [45], we wanted to confirm the higher tendency of pcp for metal chelation compared to the pc2p ligand. Only in three cases out of 28, pcp does not chelate to at least one metal center. The result is reversed for pc2p (2 out of 7). The two examples are with a 2,2’-bipy co-ligand where they leave free only the cis positions around the metal center for the metal coordination of the pc2p [20]. Another geometrical parameter is also investigated, namely the CPPC dihedral angle between the two phenyl rings bonded to the phosphorus atoms. For the 37 examples found, the average value is 28° for pcp with only three outliers with angles greater than 110°. Again, for pc2p, the result is reversed. The mean value for the angle is 148° (15 examples) with only an outlier with an angle of 18°. So, the different behavior in metal coordination as well as in the ability of forming network and coordination polymers can be related to the different structural capability given by the nature of the bridge between the two phosphinate groups.

4. Conclusions

Using a solvent assisted mechano chemistry synthesis, two new binary phases between copper and pc2p were been isolated. One of them was anhydrous material, while the other was found to be a peculiar 2D coordination polymer. Two square slabs were connected together by a copper metal center, forming potential voids filled by solvent water molecules. From the topological analysis, the 2D network revealed an unknown topology for coordination polymers, also when different kinds of network simplifications was considered. The thermal behavior of the two phases was studied. The collapse of the 2D network was confirmed, but the anhydrous phase obtained was different from the one directly obtained in the synthesis. A database survey on the known pcp and pc2p structures demonstrated how the nature of the bridging chain between the phosphinate group is a key factor for the resulting structure.

Supplementary Materials

The following are available online at https://www.mdpi.com/2073-4352/9/6/283/s1, Figure S1: Comparison of the calculated and experimental X-ray pattern for 1; Figure S2: Temperature-dependent X-ray powder diffraction patterns for phase 2.

Author Contributions

Conceptualization, A.I. and F.C.; investigation, A.I., G.T., A.G., F.C.; writing—original draft preparation, A.I.; writing—review and editing, A.I., G.T., A.G., F.C.

Funding

This research received no external funding.

Acknowledgments

A.I. acknowledges Carlo Bartoli for his technical assistance. The authors thank the Italian National Research Council (CNR) microscopy facility “Ce.M.E.–Centro Microscopie Elettroniche Laura Bonzi” for the experiments on Gaia 3, instrument acquired thanks to “Ente Cassa di Risparmio di Firenze” Grant Number n. 2013.0878 and Regione Toscana POR FESR 2014-2020 for the project FELIX (Fotonica ed Elettronica Integrate per l’Industria), Grant Number 6455.

Conflicts of Interest

The authors declare no conflict of interest.

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Scheme 1. Molecular drawing of bisphosphinate with different substituents.
Scheme 1. Molecular drawing of bisphosphinate with different substituents.
Crystals 09 00283 sch001
Figure 1. (a) Coordination mode of the first pc2p ligand; (b) Coordination mode of the second pc2p ligand; (c) Coordination of Cu1 and Cu2; (d) Coordination of Cu3. Color code: Cu turquoise, P purple, O red, C grey, H white. Symmetry transformations used to generate equivalent atoms: I = x, 1 + y, z; II = 1 + x, 1 + y, z; III = 1 − x, y, ½ − z; IV = 1 + x; y, z; V = x − 1, y, z; VI = x − 1, y − 1, z; VII = −x, y, ½ − z; VIII = 1 − x, y − 1, ½ − z.
Figure 1. (a) Coordination mode of the first pc2p ligand; (b) Coordination mode of the second pc2p ligand; (c) Coordination of Cu1 and Cu2; (d) Coordination of Cu3. Color code: Cu turquoise, P purple, O red, C grey, H white. Symmetry transformations used to generate equivalent atoms: I = x, 1 + y, z; II = 1 + x, 1 + y, z; III = 1 − x, y, ½ − z; IV = 1 + x; y, z; V = x − 1, y, z; VI = x − 1, y − 1, z; VII = −x, y, ½ − z; VIII = 1 − x, y − 1, ½ − z.
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Figure 2. (a) Square grid formed by Cu1 and pc2p ligands; (b) strips formed by by Cu1, Cu2 and Cu3 metal ions along a axis; (c) the packing of the 2D layers along the c axis. Color code: Cu turquoise, P purple, O red, C grey, H white.
Figure 2. (a) Square grid formed by Cu1 and pc2p ligands; (b) strips formed by by Cu1, Cu2 and Cu3 metal ions along a axis; (c) the packing of the 2D layers along the c axis. Color code: Cu turquoise, P purple, O red, C grey, H white.
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Figure 3. Schematic representation of; (a) 4 nodal network with two 3, one 4 and one 5 connected vertexes; (b) 3-nodal net with 4, 4, 5-connected vertex; (c) 4,4L62 and; (d) 3,4L156. The Cu1 node is represented in dark green, Cu3 in blue and P nodes in red.
Figure 3. Schematic representation of; (a) 4 nodal network with two 3, one 4 and one 5 connected vertexes; (b) 3-nodal net with 4, 4, 5-connected vertex; (c) 4,4L62 and; (d) 3,4L156. The Cu1 node is represented in dark green, Cu3 in blue and P nodes in red.
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Figure 4. (a) Diffraction pattern of the Cu(CH3COO)2 H2O and H2pc2p mixture, the main H2pc2p peaks in the bottom spectrum are indicated with black lines; (b) diffraction pattern of pure phase 1; (c) diffraction pattern of pure phase 2 after the adding of few drops of water; (d) diffraction pattern of a mixture of 1 and 2 after the adding of 1ml of water.
Figure 4. (a) Diffraction pattern of the Cu(CH3COO)2 H2O and H2pc2p mixture, the main H2pc2p peaks in the bottom spectrum are indicated with black lines; (b) diffraction pattern of pure phase 1; (c) diffraction pattern of pure phase 2 after the adding of few drops of water; (d) diffraction pattern of a mixture of 1 and 2 after the adding of 1ml of water.
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Figure 5. (a) TG/DTG curve of phase 1; (b) temperature-dependent X-ray powder diffraction patterns for phase 1, the peak between 6° and 8° 2θ is due to the diffraction of Kapton® polymer used as window in the Anton-Paar Hot Chamber; (c) TG/DTG curve of phase 2.
Figure 5. (a) TG/DTG curve of phase 1; (b) temperature-dependent X-ray powder diffraction patterns for phase 1, the peak between 6° and 8° 2θ is due to the diffraction of Kapton® polymer used as window in the Anton-Paar Hot Chamber; (c) TG/DTG curve of phase 2.
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Table 1. Crystal Data and Structure Refinement for 1.
Table 1. Crystal Data and Structure Refinement for 1.
Empirical formula C56 H84 Cu4 O30 P8
Formula weight 1739.15
Temperature 153(2) K
Wavelength 1.5418 Å
Crystal system Monoclinic
Space group P 2/c
Unit cell dimensionsa = 10.4000(10) Å
b = 10.355(2) Å
c = 33.277(2) Å
β = 99.033(8)°
Volume3539.2(8) Å3
Z2
Density (calculated)1.632 Mg/m3
Absorption coefficient3.793 mm−1
F(000)1792
Crystal size0.16 × 0.15 × 0.12 mm3
Theta range for data collection4.269 to 72.397°
Index ranges−12 < = h< = 12, −12 <= k<= 12, −41 <= l < = 34
Reflections collected55473
Independent reflections6660 [Rint = 0.0430]
Completeness to θ = 26.06°99.6%
Refinement methodFull-matrix least-squares on F2
Data/restraints/parameters6660/11/484
Goodness-of-fit on F21.067
Final R indices [I > 2σ (I)]R1 = 0.0287, wR2 = 0.0809
R indices (all data)R1 = 0.0337, wR2 = 0.0847
Largest diff. peak and hole0.451 and −0.621 e.Å−3
Table 2. Selected bond lengths (Å) and angles (°) for 2. Symmetry transformations used to generate equivalent atoms: #1 x + 1, y, z; #2 x, y − 1,z; #3 −x, y, −z + 1/2; #4 −x + 1, y, −z + 1/2.
Table 2. Selected bond lengths (Å) and angles (°) for 2. Symmetry transformations used to generate equivalent atoms: #1 x + 1, y, z; #2 x, y − 1,z; #3 −x, y, −z + 1/2; #4 −x + 1, y, −z + 1/2.
Cu1-O1 1.9221(15)Cu3-O31 1.9790(15)O3#2-Cu1-O7#188.89(6)
Cu1-O5 1.9258(14)P2-O4 1.5115(16)O8 -Cu2-O8#3145.44(9)
Cu1-O3#2 1.9663(15)P3-O5 1.5141(15)O8-Cu2-O20107.28(5)
Cu1-O7#1 1.9313(14)P3-O6 1.5088(15)O8-Cu2-O2186.82(6)
Cu1-O20 2.4651(14)P4-O7 1.5107(15)O8#3-Cu2-O2193.49(6)
Cu2-O8 1.9235(14)P4-O8 1.5087(15)O21-Cu2-O2089.47(5)
Cu2-O20 2.203(2)--O21-Cu2-O21#3178.95(9)
Cu2-O21 1.9938(15) O6-Cu3-O6#4179.06(9)
Cu3-O6 1.9293(14)O1-Cu1-O3#2178.36(7)O6-Cu3-O3090.47(4)
Cu3-O30 2.231(3)O1-Cu1-O589.84(6)O31-Cu3-O3092.33(5)
P1-O1 1.5115(15)O1-Cu1-O7#190.52(6)O6-Cu3-O3187.52(6)
P1-O2 1.5121(16)O5-Cu1-O3#290.95(6)O6-Cu3-O31#492.44(6)
P2-O3 1.5330(15)O5-Cu1-O7#1172.03(6)O31-Cu3-O31#4175.33(9)

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Ienco, A.; Tuci, G.; Guerri, A.; Costantino, F. Mechanochemical Access to Elusive Metal Diphosphinate Coordination Polymer. Crystals 2019, 9, 283. https://doi.org/10.3390/cryst9060283

AMA Style

Ienco A, Tuci G, Guerri A, Costantino F. Mechanochemical Access to Elusive Metal Diphosphinate Coordination Polymer. Crystals. 2019; 9(6):283. https://doi.org/10.3390/cryst9060283

Chicago/Turabian Style

Ienco, Andrea, Giulia Tuci, Annalisa Guerri, and Ferdinando Costantino. 2019. "Mechanochemical Access to Elusive Metal Diphosphinate Coordination Polymer" Crystals 9, no. 6: 283. https://doi.org/10.3390/cryst9060283

APA Style

Ienco, A., Tuci, G., Guerri, A., & Costantino, F. (2019). Mechanochemical Access to Elusive Metal Diphosphinate Coordination Polymer. Crystals, 9(6), 283. https://doi.org/10.3390/cryst9060283

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