Halogen Bonded Three-Dimensional UranylâOrganic Compounds

Subscriber access provided by OHSU WEST CAMPUS OR GRAD INST

Article

Halogen Bonded 3D Uranyl-organic Compounds with Unprecedented Halogen-halogen Interactions and Structure Diversity upon Variation of Halogen-substitution Lei Mei, Cong-Zhi Wang, Lin Wang, Yu-liang Zhao, Zhi-fang Chai, and Wei-Qun Shi Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/cg501783d • Publication Date (Web): 12 Feb 2015 Downloaded from http://pubs.acs.org on February 18, 2015

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Crystal Growth & Design is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Crystal Growth & Design

Halogen Bonded 3D Uranyl-organic Compounds with Unprecedented Halogen-halogen Interactions and Structure Diversity upon Variation of Halogensubstitution Lei Mei, †,ǁ Cong-zhi Wang,†, ǁ Lin Wang,†

Yu-liang Zhao,† Zhi-fang Chai*,†,‡ and Wei-qun

Shi*,† †

Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Institute of High

Energy Physics, Chinese Academy of Sciences, Beijing 100049,China ‡

School of Radiological and Interdisciplinary Sciences and Collaborative Innovation Center of

Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou 215123, China Keywords: Actinide • Uranyl-organic framework • Supramolecular • Halogen-halogen interaction • Quantum chemical calculation

ACS Paragon Plus Environment

1


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 34

Abstract: Actinide-based metal-organic materials have drawn much attention due to their intriguing 5f bonding properties and promising applications in nuclear fuels and other fields. Introduction of weak interactions, such as halogen bonds, into actinide-organic hybrid materials will provide them with more flexibility and dynamics. The first case of halogen bonded 3D uranyl-organic supramolecular frameworks with regular nano-scale channels has been obtained from multifunctional halogen-substituted isonicotinic acids. Distinct from conventional halogen bonded uranyl-organic frameworks, the supramolecular networks obtained here consist of threecomponent cocrystals and have been assemblied by an intensive supramolecular networks to obtain an extended 3D geometry. Moreover, secondary “X3” and “X6” halogen-halogen interactions resulting from the driving forces of primary hydrogen bonds have been found and analyzed by quantum chemical calculation, indicating their feature of weak bonding and special geometry. It is notable that this unprecedented type of “X6” synthon, especially for “Br6”, represents a new pattern of halogen-halogen interaction. When halogen-substitution of the organic precursor is changed, another type of halogen bonded and hydrogen bonded 3D uranylorganic framework with in situ formed cross-linking agents of 2D layered networks has been acquired. Finally, reversible transformation of 3D uranyl-organic supramolecular frameworks is available through loss and regain of water involving in hydrogen bonding networks and thus affords them structural dynamics.


2

Page 3 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Introduction Metal-organic materials,1-5 which show potential applications in a wide range of fields including adsorption, separation, recognition and catalysis,6-10 are usually established by strong coordination bonds between metal ions and rigid organic molecules. Introduction of flexibility and dynamism into metal-organic materials will extend topologies and functions of metalorganic materials.11-13 A strategy of using weak interactions14-19 as auxiliary linkage forces has been proved successful. Besides the wide application of hydrogen bond as weak interaction in metal-organic hybrid materials, bond

28-30

20-27

a variety of metal-organic materials incorporating halogen

have also been obtained. Halogen bond,

15-16

an important bonding force comparable

to hydrogen bonding, has been used in crystal engineering for many supramolecular systems, 3137

establishing lots of compounds with fascinating structures and outstanding properties. In contrast to the large amount of transition metal organic supramolecular materials, actinide

ions that bear intriguing 5f bonding properties and various topologies have been less investigated 38-45

in the field of metal-organic supramolecular materials. For example, for uranium, one of the

most studied actinide elements in relation to its structure diversities and close relevance to nuclear fuel cycle, much attention has been focused on extended uranyl-organic materials, whereas, endeavors on weak interactions-related uranyl-organic compounds are relatively lacked. Moreover, compared with hydrogen bonds appearing more common in metal-organic frameworks (such as uranyl isonicotinate 46), the utilization of halogen bonds is still in its infancy in terms of establishing uranyl-organic compounds.40,

42

Incorporation of halogen bonds in

uranyl-organic materials will not only enrich the library of uranyl-organic compounds based on weak interaction and provide novel uranyl hybrid supramolecular materials, but also, to a certain extent, promote a deeper understanding on halogen bond. Constructing halogen bonded uranyl-


3


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 34

organic compounds, especially those in three dimensions, will be an interesting arena for metal organic materials to explore structures with flexibility. To the best of our knowledge, however, halogen bond-based 3D uranyl-organic framework has never been documented to date possibly due to low participation of weak interactions as well as restricted coordination geometry of uranyl ion. In the light of methodology of building metal-organic frameworks (MOF), a possible approach to construct 3D supramolecular frameworks is the employment of organic ligands with multidentate bonding sites for weak interactions.

Scheme 1. Molecular structures of halogen-substituted isonicotinic acids

In this context, we explore the cooperation of halogen bonds and hydrogen bonds to construct 3D uranyl-organic supramolecular frameworks using multifunctional ligands, halogensubstituted isonicotinic acids (Scheme 1). As the building scaffold of uranyl-organic supramolecular frameworks, the isonicotinic acid moiety in the molecular structures of halogensubstituted isonicotinic acids serves as the coordination precursor for uranyl ions and contributor of hydrogen bonds, and halogen atoms as the contributors of halogen bonds. Herein, the first case of halogen bonded 3D uranyl-organic supramolecular frameworks with regular nano-scale


4

Page 5 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


channels has been obtained. Notably, both the supramolecular networks have been constructed by three different components in their cocrystal structure via a cooperation of halogen-halogen interactions and hydrogen bonds as well as secondary “X3” and “X6” (X=Cl, Br) halogenhalogen interactions. As far as we know, this unprecedented type of “X6” synthon is reported for the first time, and represents a new pattern of halogen-halogen interaction, especially for “Br6” synthon. Furthermore, structure diversity of uranyl isonicotinate compounds has been identified when halogen-substitution is varied, and another type of 3D supramolecular uranyl-organic framework with 2D layered networks has been obtained.

Experimental Section General Methods. Caution! Suitable measures for precautions and protection should be taken, and all operations should follow the criteria while handling such substances although natural uranium was used in the experiment. All chemical reagents were purchased from commercial sources and used as received. Thermogravimetric analysis (TGA) was performed on a TA Q500 analyzer over the temperature range of 20-800 °C in air atmosphere with a heating rate of 5 °C/min. Powder XRD measurements were recorded on a Bruker D8 Advance diffractometer with Cu Kα radiation (λ =1.5406 Å) in the range 5-80°( step size: 0.02º ). Solid-state fluorescence spectra were measured on a Hitachi F-4600 fluorescence spectrophotometer. ESIMS spectra were obtained with a Bruker AmaZon SL ion trap mass spectrometer (Bruker, USA). The Fourier transform infrared (FT-IR) spectra were recorded from KBr pellets in the range of 4000-400 cm-1 on at Bruker Tensor 27 spectrometer. Synthesis. The compounds 1-4 described herein were synthesized hydrothermally as the forms of yellow-green or yellow crystals under autogenous pressure by using Teflon-lined stainless-


5


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 34

steel bomb from a mixture of uranyl nitrate hexahydrate and isonicotinic acid derivatives (L1-L4) with ammonium hydroxide. A typical synthesis precedure is as follow: UO2(NO3)2·6H2O (200 µL, 0.1 mmol) were added to a suspension of isonicotinic acid precucusor (0.2 mmol) in water (1 mL) in a stainless-steel bomb. After treating with ammonium hydroxide (10 µL), the mixture was sealed, kept at 150 °C for 48 h and cooled to room temperature to give yellow-green prismlike crystals, which are suitable for X-ray Single crystal diffraction. The crystals were then filtered off, washed with water, and dried at room temperature (RT). The hydrothermal reaction of mono-chloro substituted ligands, L1’ or L1’’, with uranyl nitrate hexahydrate was performed under similar conditions as compounds 1-4 to afford yellow crystals (compound 1’) or brown crystals (compound 1’’). Moreover, different reaction temperature or time was set systematically to explore the methods of avoiding hydrolysis of chloro-substituent group. X-ray Single Crystal Structural Determination. X-ray diffraction data were all collected on a Agilent SuperNova X-ray CCD diffractometer with a Mo Kα X-ray source (λ = 0.71073 Å) or Cu Kα radiation (λ=1.5406 Å) at room temperature. Standard Agilent Crysalis software was used for the determination of the unit cells and data collection control. The crystal structures were solved by means of direct methods and refined with full-matrix least squares on SHELXL-97. The crystal data are given in Table 1. CCDC-1006404 (1), CCDC-1006405 (2), CCDC-1010189 (1’), CCDC-1010190 (1’’), CCDC-1010191 (L1’’, H-2-MC-6-MePCA), CCDC-1026410 (L3, H-3,5-DCPCA), CCDC-1026411 (3), CCDC-1026412 (4), contain 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.


6

Page 7 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Quantum chemical calculation for structure optimization and quantum theory of atoms in molecules (QTAIM) analysis. In density functional theory (DFT) calculations,47-48 scalar relativistic effects were taken into account by the quasi-relativistic effective core potentials (RECP) including 60 core electrons and the corresponding valence basis sets49-52 for uranium. The 6-31G(d) basis sets were adopted for light atoms H, C, N, O, Cl, and Br. No symmetry constraints were used for geometry optimization. The minima character of each optimized structure has been verified by harmonic vibrational frequency analysis at the B3LYP/RECP/631G(d) level of theory. Previous studies

53-57

have been found that this level of theory could

provide accurate geometries for actinide species. All these calculations were performed with the Gaussian 09 program package.58 For the analysis of “X3” and “X6” synthons, DFT calculations using the Gaussian 09 package were carried out for the model fragments of 1 and 2 using the M06-2X functional.49 Previous studies49-52 have been found that the M06-2X method could give good results for complexes with noncovalent interactions. It has been found that diffuse functions are important to obtain considerably better results for weakly bound systems.59-62 The 6-311+G(d, p) basis sets were adopted for light atoms H, C, N, O, Cl and Br, while for uranium the same basis set as used for structure optimization is also used here. Single point calculations have been carried out at the M06-2X/RECP/6-311+G(d, p) level of theory based on the model fragments from the experimental crystal structures of 1 and 2. At the same level of theory, the quantum theory of atoms in molecules (QTAIM)

63-66

analysis has been carried out with the Multiwfn 3.3.3

package.67


7


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 34

Table 1. Crystal data and structure refinement for uranyl compounds 1-4. 1

2

formula

C36H22Cl12 N6O20U2

C36H22Br12N6O20U2

C11H6Cl4N2O5U

C11H6Br4N2O5U

formula weight

1760.06

2293.58

626.01

803.81

crystal system

triclinic

triclinic

orthorhombic

orthorhombic

space group

_

_

P1

P1

Ibca

Ibca

a, Å

9.3767(4)

9.5038(5)

8.2621(6)

8.3785(3)

b, Å

10.8827(5)

11.1204(6)

19.3780(15)

19.4370(8)

c, Å

12.9208(5)

13.0924(6)

21.87(2)

22.0629(10)

α, deg

88.646(3)

89.259(4)

90

90

β, deg

86.652(3)

86.419(4)

90

90

γ, deg

89.268(4)

88.384(5)

90

90

1315.79(10)

1380.33(13)

3502(3)

3593.0(2)

1

1

8

8

293

293

293

293

V, Å

3

Z T, K 3

3

4

2.221

2.759

2.375

2.972

µ (mm )

a

a

b

b

R1, wR2 [I ≥ 2σ(I)]

0.0286, 0.0551

0.0277, 0.0661

0.0445 , 0.1271

0.0285, 0.0643

R1, wR2 (all data)

0.0364, 0.0588

0.0305, 0.0680

0.0556, 0.1530

0.0355, 0.0682

Dc, g/cm -1

a

23.503

27.238

9.901

17.953

b

µ (Cu Kα,). µ (Mo Kα,).

Results and Discussion Structure description. [(UO2)2(2,6-DCPCA)4(H2O)2]·(H-2,6-DCPCA)2·(H2O)2 (1): Compound 1，prepared from 2,6-dichloroisonicotinic acid (H-2,6-DCPCA, L1, see Scheme 1), crystallizes in the triclinic _

space group P 1 as a cocrystal. It contains three components, that are dimeric uranium unit, free H-2,6-DCPCA molecules and solvate water molecules (Figure 1), respectively. The dimeric


8

Page 9 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


uranium unit is composed of two monomeric uranyl cations bridged through the µ2-(O, O)carboxylic acid groups, and each uranyl further coordinates with a water molecule and a η2-mode carboxylic group to form a pentagonal bipyramid geometry with equatorial U-O distances from 2.316(4) to 2.469(4) Å (Figure 1 and Table 2). Though the dimeric uranyl coordination pattern is similar to that observed in the uranyl complexes of 4-halobenzoic acids42, the overall configurations of dimer in 1 is quite different: the H-2,6-DCPCA ligand prefers good coplanarity, while the 4-halobenzoic acid results in a bend out of plane. DFT calculations were carried out to optimize the geometrical structure of the dimer (see the Supporting Information, Figure S1a) and the result is in good accordance with the experimental structure in crystal (Table S1), indicating different coordination feature of 2,6-DCPCA from simple halogen-substituted benzoic acid.

Figure 1. The asymmetric unit of 1 containing three components and coordination sphere of dimeric uranium unit.


9


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 34

Figure 2. An extended one-dimensional chain linked by ditopic Cl-Cl interactions of type I (a) and threedimensional uranyl-organic supramolecular framework with regular nano-scale channels (b).

Based on the coplanar configuration, the outward halogen atoms in each dimer associate with adjacent dimmers by ditopic halogen-halogen interactions to obtain an extended one-dimensional chain (Figure 2a). The Cl-Cl distance of 3.416(3) Å is shorter than the sum of van der Waals radii (ca. 3.6 Å ), and the C-Cl···Cl angles (θ1 and θ2) of 170.26(21)˚ and 161.02(20)˚ are approximately equal, indicating that the halogen-halogen interaction is of type-I.68-69 Besides the uranyl dimer in cocrystal 1, another two components, non-coordinated H-2,6-DCPCA and water molecules are included, which insert into the voids of adjacent one-dimensional chains of uranyl


10

Page 11 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


dimers to build up a 3D uranyl-organic supramolecular framework with two types of regular nano-scale channels in sizes of 10.5*5.5 Å and 14.0*4.0 Å by hydrogen bonds and halogen bonds (Figure 2b).

Table 2. Selected uranium-related bond distances (Å) and distances between the donors and acceptors of hydrogen bonds (Å) observed in uranyl compounds 1-4.

U(1)-O(1) U(1)-O(2) U(1)-O(3) U(1)-O(4) U(1)-O(5) U(1)-O(6) U(1)-O(7)

2.469(4) 2.439(4) 2.316(4) 2.337(4) 2.427(4) 1.755(4) 1.752(3)

U(1)-O(1) U(1)-O(2) U(1)-O(3) U(1)-O(4) U(1)-O(5) U(1)-O(6) U(1)-O(7)

2.464(4) 2.431(4) 2.314(4) 2.331(5) 2.433(4) 1.751(5) 1.765(4)

U(1)-O(1) U(1)-O(2) U(1)-O(3)

2.276(3) 2.732(9) 1.584(8)

U(1)-O(1) U(1)-O(2) U(1)-O(3)

2.297(2) 2.487(4) 1.762(4)

1 O(5)-H(5A)···N(3) O(9)-H(9)···O(1w) O(1w)-H(1wA)···O(6) O(1w)-H(1wB)···N(1) C(9)-H(9A)···O(6) C(12)-H(12)···O(1) C(18)-(18)···O(2) 2 O(5)-H(5B)···N(2) O(8)-H(8)···O(1w) O(1w)-H(1wA)···O(7) O(1w)-H(1wB)···N(3) C(17)-H(17)···O(7) C(14)-H(14)···O(1) C(4)-H(4)···O(2) 3 U(1)-N(1) N(2)-H(2) ···O(1) C(7)-H(7) ···O(3) 4 U(1)-N(1) N(2)-H(2) ···O(1) C(7)-H(7) ···O(3)

2.810(6) 2.597(6) 2.916(6) 2.960(7) 3.333(7) 3.522(7) 3.246(7) 2.885(6) 2.621(7) 2.914(6) 3.017(7) 3.309(8) 3.613(7) 3.277(7) 2.890(16) 2.399(18) 3.109(22) 2.597(8) 2.720(11) 3.506(13)


11


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 34

Figure 3. Local stacking model of 1 with H-2,6-DCPCA molecules (bolded) filling in a typical cavity around four adjacent uranyl dimmers (top), and hydrogen-bond networks of H-2,6-DCPCA facing down (bottom).

A local stacking model containing two H-2,6-DCPCA and two water molecules (bolded, facing down and up) filling in a typical cavity around four adjacent uranyl dimmers (Figure 3) is subtly selected and a structural analysis is made in detail to figure out how the hydrogen bonds and halogen bonds work. It was noticed that all the carboxylic acids filling into the voids incline from the one-dimensional halogen-halogen bonded chains with an angle of ca. 47.65˚. As shown in Figure 3, the H-2,6-DCPCA facing down interacts with O(5)-H(5A) belonging the coordinated H2O of uranyl dimer nearby in layer B through N(3) atom. From the opposite direction, it hydrogen-bonds to the free water (O(1w)) by the carboxylic acid group and subsequently link to


12

Page 13 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


another two neighbored dimers (in layer A and B) via O(1w)-H···N(1) and O(1w)-H···O(6) hydrogen-bonding. Moreover, another two C-H···O hydrogen bonds, C(9)-H···O(6) and C(12)H···O(1), increase the complexity of hydrogen-bond networks. Similarly, the other H-2,6DCPCA in the same cavity, which faces up, interacts with the neighbored chains of uranyl dimers by hydrogen-bond networks from an inverse direction. Further analysis on the packing mode of these inserted H-2,6-DCPCA molecules reveals an interesting phenomenon: besides extensive participation in hydrogen bonding, both the halogen atoms of each H-2,6-DCPCA molecule also locate precisely near the halogen atoms of uranyl dimers in different layers to form a asymmetric triangular “Cl3” with three vertical angles of 63.65(5)˚, 68.41(5)˚ and 47.94(4)˚ and a centrosymmetric hexagonal cyclic “Cl6” synthon bearing three different angles of 139.41(6)˚,144.99(6)˚ and 72.30(5)˚, respectively (Figure 4a). Although “Cl3” synthon is commonly observed in many systems of halogen organic derivatives, as far as we know, this unprecedented “Cl6” synthon here is observed for the first time, which represents a new type of halogen-halogen interaction. This special location of H-2,6-DCPCA molecule results in crosslinking by intra-sheet “Cl3” synthon and inter-sheet “Cl6” synthon in one layer of uranyl sheets (Figure 4b). Compared to the distance of ditopic Cl-Cl interaction, the newly-built edge lengths in “Cl3” synthon are slightly longer (Table 3), while those in “Cl6” synthon with the shortest distance of 3.668(3) Å are closer to the sum of the van der Waals radii. Moreover, the C-Cl···Cl angles for the “Cl3” and “Cl6” synthons are different from those observed in type-I or type-II of halogen-halogen interactions. Based on the longer distances of Cl-Cl as wll as anomalous C-X···X angles, these two type of bonding created by inserted H-2,6DCPCA should be a secondary interaction resulting from the driving forces of primary hydrogen bonds.


13


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 34

Figure 4. Asymmetric triangular “Cl3” synthon and centrosymmetric hexagonal cyclic “Cl6” synthon originated from inserted H-2,6-DCPCA molecules in two adjacent layers (a) and in one layer (b) of onedimensional halogen-halogen bonded chains. For (a), the motifs in blue and pink colours represent different layers of one-dimensional chains.


14

Page 15 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 3. X-X bond distances (Å) and angles (deg) of halogen bonds observed in uranyl compounds

Compound/Type pe\\ “Cl3” 1 “Cl6”

“Br3” 2 “Br6” 3

4

X-X interaction pattern

X-X distance/Å

C-X···X angles/˚

C(5)-Cl(3)···Cl(6)-C(13)

4.123(2)

93.71(22)

C(5)-Cl(3)···Cl(2)-C(20)

3.416(3)

170.26(21)

C(20)-Cl(2)···Cl(6)-C(13)

4.278(2)

117.24(21)

C(1)-Cl(4) ···Cl(1)-C19

4.017(3)

151.54(21)

C(1)-Cl(4) ···Cl(5)-C15

3.668(3)

122.53(23)

C(19)-Cl(1)···Cl(5’)-C(15’)

4.028(3)

135.73(22)

C(6)-Br(2)···Br(3)-C(15)

3.406(1)

156.61(17)

C(6)-Br(2)···Br(6)-C(12)

4.149(1)

93.24(17)

C(15)-Br(3)···Br(6)-C(12)

4.057(1)

118.72(18)

C(9)-Br(1)···Br(4)-C(22)

3.867(1)

153.13(18)

C(9)-Br(1)···Br(5)-C(11)

3.850(1)

121.17(20)

C(22)-Br(4)···Br(5’)-C(11’)

3.945(1)

136.72(17)

C(6)-Cl(2)···Cl(1)-C(3)

3.585(8)

163.05(65)

C(6)-Cl(2)···Cl(1’)-C(3’)

3.827(8)

124.22(64)

C(6)-Br(2)···Br(1)-C(3)

3.619(2)

168.17(29)

C(6)-Br(2)···Br(1’)-C(3’)

3.724(2)

117.94(29)

UO2(2-MHPCA)2 (1’): Reaction of uranyl nitrate hexahydrate with 2-chloroisonicotinic acid (H-2-MCPCA, L1’) under hydrothermal condition similar to 1 affords the uranyl compound 1’. The structure of compound 1’ is composed of a uranyl center in pentagonal bipyramid geometry, which is coordinated to a η2-carboxyl group, a η1-carboxyl group and two hydroxyl groups from four 2-hydroxyisonicotinate (2-MHPCA) motifs to form a 2D wave-shaped network with intrasheet hydrogen bonds (Figure S5). It is interesting to note that there is no chlorine atom in the structure of compound 1’, and instead, hydroxyl oxygen atom takes the place of chlorine, indicating the hydrolysis of chlorine under hydrothermal condition may produce a 2-MHPCA


15


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 34

molecule as a real ligand of uranyl cation. This phenomenon of hydrolysis is further proved by a minor amount of colorless needle-like crystals in the hydrothermal product, which give the MS peak (m/z) of 139.87 in ESI-MS, corresponding to the molecular ionic peak of hydrolyzed ligand ([C6H5NO3+H]+). Besides, the loss of fluorescence is another evidence for the adduction of hydroxyl groups resulting from the hydrolysis of chlorine, as the coordination of a hydroxyl group to the uranyl cation could quench the fluorescence through a nonradiative decay mechanism induced by the oscillation of OH bonds (see the Supporting Information, Figure S7).70 Moreover, only one obvious weight loss in thermogravimetric analysis indicates its good structural stability based on 2D coordination networks, which should be in close relation to the cross-linking capacity of hydroxyl groups (Figure S8). [UO2(2-MH-6-MePCA)(H2O)(ox)0.5]·(H2O)2 (1’’): When another analogue of H-2,6-DCPCA, named as 2-chloro-6-methylisonicotinic acid (H-2-MC-6-MePCA, L1’’), was used to react with uranyl nitrate under similar hydrothermal condition, compound l’’ could be obtained. In the crystal structure of 1’’, the chlorine-substituted H-2-MC-6-MePCA precursor can also undergo a hydrolysis into 2-hydroxy-6-methylisonicotinate (2-MH-6-MePCA), and even, another oxalate (ox) ligand formed in situ can be found (Figure S9). The oxalate ligand takes part in the coordination of uranyl cation in a bridging pattern to form a uranyl dimer, which further interconnects each other through the bidentate 2-MH-6-MePCA to obtain 1D extended chain (Figure S9) with intra-chain hydrogen bonds between adjacent dimers (O(4)-H(4B)···O(8), Table S3) for structure stabilization. Moreover, the 1D extended chain can be weaved into a 3D network via two types of inter-chain hydrogen bonding as well as pi-pi stacking (Figure S10). [(UO2)2(2,6-DBPCA)4(H2O)2]·(H-2,6-DBPCA)2·(H2O)2 (2): Compound 2 affords a similar cocrystal structure (Figure 5a) using 2,6-dibromoisonicotinic acid (H-2,6-DBPCA, L2) as the


16

Page 17 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


hydrothermal reaction precursor. The carboxyl-bridged uranyl dimer species with typical equatorial U-O distances from 2.314(4) to 2.464(4) Å also show good coplanarity (Figure 5a and Table S1) and mutually linked with adjacent units to form an extended 1D chain by halogenhalogen interactions of type I, where the Br-Br distance is 3.406 Å and the approximately equal C-X···X angles are 156.60˚ and 168.40˚. It is notable that, the shortening of Br-Br distance (~0.40 Å ) compared with the sum of the van der Waals radii in compound 2 is greater than that of Cl-Cl distance (~0.18 Å ) in compound 1, suggesting stronger halogen-halogen interaction for this bromide analogue. As expected similar to 1, free carboxylic acid and water molecules crosslink the onedimensional chains of uranyl dimmers by hydrogen bonds and halogen bonds to make out a 3D framework with regular nano-scale channels (10.8*5.5 Å and 14.2*4.1 Å ) (Figure 6). The inclined angle of 51.65˚ between the inserted carboxylic acid and the one-dimensional chains is slightly different to that in 1. A crisscrossed hydrogen-bond network as well as unique triangular “Br3” and hexagonal cyclic “Br6” joints are responsible for the construction of 3D supramolecular framework. Again, stronger halogen-halogen interaction for the bromide analogue is observed as indicating by the smaller difference of Br-Br distances from the sum of the van der Waals radii in “Br3” or “Br6” joints than those in “Cl3” and “Cl6” joints (Table 3).


17


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 34

Figure 5. The asymmetric unit and coordination sphere of dimeric uranium unit of 2 (a) and the onedimensional extended chain (b).


18

Page 19 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 6. Top: 3D uranyl-organic supramolecular framework of 2 (a) and a local stacking model with H-2,6DBPCA molecules (bolded) filling in a typical cavity around four adjacent uranyl dimmers (b). Bottom: hydrogen-bond networks of H-2,6-DBPCA facing down (c), and the “Br3” and hexagonal cyclic “Br6” synthon in one layer (d).

[(UO2)O(3,5-DCPCA)]·(H-3,5-DCPy)

(3):

Compound

3

was

prepared

from

3,5-

dichloroisonicotinic acid (H-3,5-DCPCA, L3), a position isomer of H-2,6-DCPCA. Two independent components, that are uranyl-organic moiety and 3,5-dichloropyridinium, are included in compound 3 (Figure 7a). In the uranyl-organic moiety, the uranyl cation exhibits a pentagonal bipyramid geometry with an equatorial plane in “NO4“ coordination pattern, which


19


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 34

contains not only carboxyl group but also nitrogen atom in the pyridine ring of 3,5-DCPCA (Figure 7b). Another two coordinated oxygen atoms in the equatorial plane serve as cornersharing atoms to interconnect the adjacent uranyl polyhedral in trans position, resulting in an infinite chain. The 1D chain of multi-nuclear uranyl further extends to a twodimensional layered network through the connection of the bidentate 3,5-DCPCA linkers (Figure 7c). Besides the uranyl-involving moiety, the other part in the structure of 3 is 3,5dichloropyridinium, which result from in situ decarboxylation of the H-3,5-DCPCA precursor. These discrete 3,5-dichloropyridinium (H-3,5-DCPy) molecules fill as the template in the gaps between two adjacent layers of uranyl-organic network and interact with the layers by halogen bonding and hydrogen bonding to make a three-dimensional framework. As shown in Figure 8, the distance of 3.585(8) Å between the chlorine atom (Cl(2)) of 3,5-dichloropyridinium and the closest Cl(1) atom in uranyl-organic network is shorter than the sum of the van der Waals radii, indicating the existence of halogen-halogen interaction, and this interaction can be attributed to type II based on the C-Cl···Cl angles of 163.05(65)˚ and 81.36(49)˚ (Table 3). Meanwhile, the interaction is enhanced by hydrogen bonding of the C-H moiety to the axial O(3) atom of uranyl. Moreover, the N-H of 3,5-dichloropyridinium molecule hydrogen-bonds to the adjacent layer from the opposite direction via the corner oxygen, O(1). In all, the 3,5-dichloropyridinium molecule crosslinks the layered struture by combination of halogen bonds and hydrogen bonds, and the resulting structure has been characterized (Figure S11-S13).


20

Page 21 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 7. Two discrete components involving in 3 (a), coordination sphere of the uranium unit (b), and 2D layered network constructed by the connection of the bidentate 3,5-DCPCA linkers (c).

Figure 8. Halogen bonded and hydrogen bonded 3D supramolecular framework with discrete 3,5dichloropyridinium (H-3,5-DCPy) molecules filling in the gaps as linkers.


21


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 34

Figure 9. Halogen bonded and hydrogen bonded 3D supramolecular framework of compound 4 with discrete 3,5-dibromopyridinium (H-3,5-DBPy) molecules filling in the gaps as linkers.

[(UO2)O(3,5-DBPCA)]· (H-3,5-DBPy) (4): Compound 4 has been fabricated from the bromine-substituted analogue of H-3,5-DCPCA, 3,5-dibromoisonicotinic acid (H-3,5-DBPCA, L4). Similar to 3, the crystal structure of 4 contains two components, that are uranyl-organic moiety and 3,5-dibromopyridinium (Figure S14). In the uranyl-containing moiety, the nitrogen atom in the pyridine ring of 3,5-DBPCA also coordinates to uranyl center with a “NO4“ equatorial plane, and combines with carboxyl group to interconnect the infinite cornersharing uranyl chain and bulid up a similar 2D network. The 2D network is further interacts with 3,5-dibromopyridinium located within the layers by weak interactions (Figure 9). Hydrogen bonds related with C(7)-H and N(2)-H of 3,5-dibromopyridinium link the neighbouring layers from different directions, while halogen-halogen interactions are only found in one side, where each bromine atom of 3,5-dibromopyridinium interacts with two adjacent halogen-involving linkers bearing the Br-Br distances of 3.619(2) and 3.724(2) Å , respectively. Both the halogen-


22

Page 23 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


halogen interactions here can be assigned to type II, according to C-X···X angles, where one set is 168.17(29)˚ and 88.44(19)˚, and the other is 117.94(29)˚ and 153.73(20)˚. Quantum chemical calculation and quantum theory of atoms in molecules (QTAIM) analysis of “X3” and “X6” synthons. As depicted in quantum theory, the existence of bond critical point (BCP) is one of the most important indicators for interatomic bonding interactions and the electron density (ρ) properties at BCP afford a characterization of the interactions.63-66 In the inquiry for a better insight into the nature of “X3” and “X6” synthons of halogen-halogen interaction found in these complexes, quantum theory of atoms in molecules (QTAIM) analysis was carried out in simplified molecular models of “X3” and “X6” at the M06-2X/RECP/6311+G(d, p) level of theory. The BCPs referring to the X···X bonding interactions are clearly observed for “X3” and “X6” of compound 1 or 2 (See the Supporting Information, Figure S15). At the BCPs, the electron density (ρ), Laplacian of electron density (∇2ρ), the kinetic (G) and potential (V) energy density have been determined (Table 4). For the X···X bonding with shorter interatomic lengths (Rij) of 3.416/3.406 and 3.668/3.850 Å, the ρ, ∇2ρ, G and V values (0.04

Halogen Bonded Three-Dimensional UranylâOrganic Compounds

Recommend Documents

Halogen Bonded Three-Dimensional UranylâOrganic Compounds