Inclusion of the dithiadiazolyl radical PhCNSSN• into the dynamically porous metallocycle [Cu2(L1)2Cl4], where L1 is the bidentate ligand 1,3-bis(imidazol-1-ylmethyl)-2,4,6- trimethylbenzene, has been achieved by gas phase diffusion. Single crystal X-ray diffraction, powder X-ray diffraction, UV-visible spectroscopy, EPR and SQUID magnetometry studies confirm inclusion of the radical into this seemingly non-porous material, and illustrate the presence of antiferromagnetic coupling between the paramagnetic host and guest species. The radical guest is readily released by heating or by the addition of solvent (CH2Cl2)

Arauzo, Ana

Barbour, Leonard J.

Campo, Javier

Haynes, Delia A.

Nikolayenko,, Varvara I.

Rawson, Jeremy M.

English

Inclusion of the dithiadiazolyl radical PhCNSSN˙ into the dynamically porous metallocycle [Cu2(L1)2Cl4], where L1 is the bidentate ligand 1,3-bis(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene, has been achieved by gas phase diffusion. Single crystal X-ray diffraction, powder X-ray diffraction, UV-visible spectroscopy, EPR and SQUID magnetometry studies confirm inclusion of the radical into this seemingly non-porous material, and illustrate the antiferromagnetic coupling between the paramagnetic host and guest species. The radical guest is readily released by heating or by the addition of solvent (CH2Cl2).We thank the National Research Foundation of South Africa and Stellenbosch University for funding. J. M. R. acknowledges the support of the Canada Research Chair Program. J. C. acknowledges the Grant No. MAT2015-68200-C2-2-P from the Spanish Ministry of Economy and Competitiveness.Peer reviewe

Nikolayenko, Varvara I.

Arauzo, Ana B.

Digital.CSIC

Published as: Chem Comm, 2017, 53, 11310 - 11313 COMMUNICATION This journal is © The Royal Society of Chemistry 20xx J. Name., 2013, 00, 1-3 | 1Please do not adjust margins Please do not adjust margins Received 00th January 20xx, Accepted 00th January 20xx DOI: 10.1039/x0xx00000x www.rsc.org/ Inclusion of a dithiadiazolyl radical in a seemingly non-porous solid Varvara I. Nikolayenko,a Leonard J. Barbour,a Ana Arauzo,b Javier Campo,b Jeremy M. Rawsonc and Delia A. Haynes*a Inclusion of the dithiadiazolyl radical PhCNSSN• into the dynamically porous metallocycle [Cu2(L1)2Cl4], where L1 is the bidentate ligand 1,3-bis(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene, has been achieved by gas phase diffusion. Single crystal X-ray diffraction, powder X-ray diffraction, UV-visible spectroscopy, EPR and SQUID magnetometry studies confirm inclusion of the radical into this seemingly non-porous material, and illustrate the presence of antiferromagnetic coupling between the paramagnetic host and guest species. The radical guest is readily released by heating or by the addition of solvent (CH2Cl2). The evolution and exploitation of host–guest interactions for use in gas sequestration and storage,1,2 chemical sensing,3-5 and heterogeneous catalysis6-8 have garnered considerable interest in recent years owing to the rapid expansion of the number of known dynamically porous solid-state materials.9 As this field of chemistry becomes more established, researchers are focussing on property development, including magnetic behaviour, light modulation, spin-state bistability, electron, hole and ion mobility, ferroelectricity and luminescence. Each of the aforementioned properties is governed by host–guest interactions: sensors require one entity to impose some measurable change on the other, for example,10 while orientation-specific binding can lead to regio- and/or enantioselective transformations in catalysis.11 The inclusion of radical guest molecules into porous materials such as hydrogen-bonded frameworks (HOFs), metal-organic frameworks (MOFs) or discrete cavities (such as those found in metallocycles) offers the potential for strong host-guest and guest-guest electronic interactions, potentially resulting in interesting magnetic or transport properties. The majority of known HOF-radical inclusion compounds were obtained by co-crystallisation of the guest with an organic host from solution or the gas phase.12-17 A recent review by D'Alessandro et al. illustrates the increase in reports of MOFs containing radical moieties, either incorporated into the host backbone or as encapsulated guests.18 However, the number of reported inclusion compounds containing paramagnetic guests still remains low. In fact, there are only two reports of the inclusion of thiazyl radicals into metal-containing frameworks, both arising from our groups, and both involving diamagnetic host frameworks. One study reports the inclusion of benzodithiazolyl and methylbenzodithiazolyl into MIL-53(Al),19 while the other reports the inclusion of PhCNSSN• into Faujasite.20 Notably, in the former complex the walls of the host cavity rotate to accommodate the guest, indicating a responsive relationship between the host and the guest. Previous studies in the Barbour group21 have shown the copper metallocycle [Cu2(L1)2Cl4] (Scheme 1, hereafter 1a) to be a dynamic material, capable of undergoing multiple single crystal-to-single crystal (SC-SC) guest-inclusion reactions. A variety of guests have been included in the metallocyclic host, yielding host-guest systems 1-11, where the host adapts the size of the cavity to best suit a particular guest via rotation of the imidazole rings.21 Since 1a is a highly stable, dynamic host that is inherently paramagnetic, we decided to investigate inclusion of a thiazyl radical (4-phenyl-1,2,3,5-dithiadiazolyl, PhCNSSN•, Scheme 1) into this material, with the aim of inducing communication between the spin on the host and the spin on the guest. Since guest encapsulation is accompanied by cooperative motion of the host, inducing a highly specific change in the solvent-accessible space and in turn in the chemical environment of the metal, single-crystal (SC) X-ray data in conjunction with variable temperature solid-state EPR were employed to obtain a clearer understanding of the host-guest interaction. a. Department of Chemistry and Polymer Science, Stellenbosch University, P. Bag X1 Matieland, 7602, Stellenbosch, South Africa. E-mail: dhaynes@sun.ac.za. b. Aragón Materials Science Institute (CSIC-University of Zaragoza) and CondensedMatter Physics Dept. Facultad de Ciencias, 50009 Zaragoza (Spain) c. Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor, ON, Canada N9B 3P4 Electronic Supplementary Information (ESI) available: [Full experimental details,synthesis, TGA, DSC, EPR SQUID and DFT; CCDC deposition numbers 1566860-1566863 ]. See DOI: 10.1039/x0xx00000x COMMUNICATION Journal Name 2 | J. Name., 2012, 00, 1-3 This journal is © The Royal Society of Chemistry 20xx Please do not adjust margins Please do not adjust margins The host was prepared as its methanol solvate 1, following the previously reported synthesis,21 and was activated by heating under dynamic vacuum at 100 °C for 24 hours to eliminate the included methanol, yielding the apohost 1a. Bulk phase purity was established using powder X-ray diffraction (Figure S2). Previous work conducted by Barbour, Haynes and co-workers has shown that materials that are solid but sufficiently volatile at room temperature can be included into framework hosts by sorption of the guest directly from the gas phase.19,21,22 This is also possible for metallocycles such as 1a.21 The volatility of PhCNSSN• permitted its inclusion into the apohost 1a when the two species were heated together in vacuo at 80 °C. (Figure S1). After 24 hours of exposure to vapours of the radical, crystals of 1a had undergone a distinct colour change from green to deep red (almost black), 12 (Figure 1). The UV absorption spectra of the two samples (Figure S9) confirm the observed colour change, with 1a absorbing the majority of the visible spectrum except in the green region, while 12 does not transmit any light. The powder pattern of bulk 12 is similar to that of 1a (Figure S3), albeit with some small differences in peak positions/intensities, indicating that the radical has been included in the host without significant structural changes to the crystal structure. Notably there is no evidence for neat PhCNSSN• in the PXRD, confirming that the observed colour change is not as a result of crystallisation of the radical on the surface of the host crystals. The structure of 12 was elucidated by means of single-crystal X-ray diffraction, as inclusion of the radical is a SC-SC process (Table S1). The structure shows that the space group of the host (P21/c) is maintained in 12, but there is an increase in the length of the b axis, with a corresponding increase in the unit cell volume. In addition to the metal, ligand and chloride counterions present in the asymmetric unit of 1a, the asymmetric unit of 12 also contains one dithiadiazolyl radical, which is disordered across an inversion centre with a site occupancy of ca. 30%, resulting in a guest occupancy of ca. 60%. Closer examination of the two crystal structures determined at 100 K (Figure 1) shows notable diﬀerences in the Cu―Cu distances, as well in the phenyl(centroid)―phenyl(centroid) and imidazole(centroid)―imidazole(centroid) distances. In order to accommodate the radical guest, the copper metallocycle expands along the shorter dimension (Cu-Cu), while contracting along the longer dimension (phenyl-phenyl). In 12, one of the two imidazole moieties is disordered over two positions with the minor fragment having a site occupancy of 30%. This disorder is attributed to weak hydrogen bonding between the nitrogen atom of the radical guest and the hydrogen atom of the host imidazole. Extension of the ASU shows the radicals encapsulated within stacks of metallocycles (Figure 2). Guest inclusion results in two cavities within the host merging, analogous to the behaviour of the host on inclusion of naphthalene.21 Merged cavities are separated from one another because the radical guest is too large to be included between every metallocycle pair. however, the Cu…Cu distances between metallocycles remain constant along the metallocycle stack (Fig. 2b). The distortion of the host lattice is manifested in a subtle change in the coordination geometry at the four-coordinate copper(II) centre. For the host complex, the τ4 parameter (defined as [360 – (α + β)]/141 where α and β are the two largest angles subtended at Cu) is 0.37, intermediate between square-planar (τ4 = 0) and tetrahedral (τ4 = 1) geometries. In 12 the geometry at Cu is slightly more compressed towards square planar (τ4 = 0.32). No degradation of 12 was noted using PXRD or EPR, even when samples had been exposed to air in ambient conditions for extended periods of time (Figure S4). This enhanced stability of the radical within the metallocycle is in stark contrast to the pure radical, which degrades when not kept under an inert atmosphere. In addition, TGA data show no significant mass loss for 12 up to 100 oC (Figure S5). These findings are consistent Journal Name  COMMUNICATION This journal is © The Royal Society of Chemistry 20xx J. Name., 2013, 00, 1-3 | 3Please do not adjust margins Please do not adjust margins with previous studies, where thiazyl radicals included in porous materials were shown to be stable for up to a month.19 Solid-state EPR spectroscopy was used to further probe the structures of both 1a and the new radical-containing paramagnetic hybrid material 12. Both 1a and 12 yield essentially axial spectra with a small rhombic distortion (Fig. 3, ESI). Previous EPR studies on distorted CuCl42- anions (0.72 > τ4 > 0.61; where τ4 is defined as [360 – (α + β)]/141 where α andβ are the two largest angles subtended at Cu23) producerhombic spectra with g|| > g⊥ with increasing distortionstowards square planar, leading to a reduction in the magnitudeof the g-tensor.24 In this context it is notable that both 1a and12 also exhibit g|| > g⊥, with smaller g-values for 12, which iscloser to square planar. The average g-values for 1a and 12 (2.12and 2.11, respectively) are smaller than those for CuCl42-,consistent with geometries significantly closer to square planar(τ4 = 0.37 and 0.32). Notably the EPR spectrum of 12 does notexhibit an observable component associated with the PhCNSSNradical (g = 2.01).The EPR linewidth of the radical inclusion complex is substantially greater than that of the host framework, which can be attributed to dipolar broadening between radical and host, or through some exchange interaction, such that the radical no longer behaves as an isolated S = ½ spin system. The presence of the radical in the host framework was confirmed by displacement of the guest by addition of CH2Cl2 (Fig. 3c). To examine the nature of the host-guest interaction, variable temperature dc SQUID magnetometry measurements were made on 1a and 12. The parent host framework was found to exhibit Curie-Weiss paramagnetism across the range 1.8 – 300 K with C = 0.842 emu K mol-1 and θ = -2.0 K, consistent with very weak antiferromagnetic interactions between two S = ½ ions with g = 2.12, in agreement with the value determined by EPR spectroscopy (2.12). M vs H studies at 1.8 and 10 K are nicely replicated with two S = ½ ions using g = 2.12 and a mean field correction term to take into account weak anti-ferromagnetic interactions (θ = -0.95 K, see ESI). Radical inclusion leads to a marked change in the paramagnetism of the sample. Down to 50 K the magnetism once again follows Curie-Weiss behaviour but the Curie constant is a little larger (C = 0.954 emu K mol-1), consistent with an increase in the total number of spin centres in the sample. The Curie constant equates to 24% S = ½ (based on TGA data on the same sample recorded after the SQUID measurements) with g = 2.0 and two S = ½ Cu2+ centres with g = 2.15. The Weiss constant (θ = -5.7 K), reflects weak antiferromagnetic interactions which could comprise both host-host and host-guest interactions. A subtle change in gradient is observed below 20 K (C = 0.772 emu K mol-1, θ = -0.63 K), consistent with antiferromagnetic coupling between host Cu2+ ions and the guest PhCNSSN radicals. This interpretation is supported by DFT calculations (see ESI), which reveal exchange couplings between the radical and Cu2+ of -11 and -12 cm-1 for the two copper atoms in the metallocycle. In conclusion, the incorporation of a dithiadiazolyl radical into the dynamic paramagnetic metallocycle 1a results in an unusual paramagnetic hybrid material, 12, in which SQUID and DFT studies support the presence of exchange coupling between host and guest. The stability of the radical is significantly enhanced by inclusion in the metallocyclic host. There are no conflicts of interest to declare. We thank the National Research Foundation of South Africa and Stellenbosch University for funding. J.M.R. acknowledges the support of the Canada Research Chair Program. J.C. acknowledges the Grant No. MAT2015-68200- C2-2-P from the Spanish Ministry of Economy and Competitiveness. Fig. 4 Temperature dependence of χT for 1a (blue circles) and 12 (purple circles). The inset is an expansion of the data between 0 and 50 K.0.00.20.40.60.81.00 100 200 300χT (emu.K.mol-1)Temperature (K)121a121ab) 12 a) 1a c)COMMUNICATION Journal Name 4 | J. Name., 2012, 00, 1-3 This journal is © The Royal Society of Chemistry 20xx Please do not adjust margins Please do not adjust margins Notes and references 1 H. Wu, W. Zhou and T. Yildirim, J. Am. Chem. Soc., 2007,129, 5314. 2 K. Sumida, D. L. Rogow, J. A. Mason, T. M. McDonald., D. Bloch, Z. R. Herm, T.-H. Bae and J. R. Long, Chem. Rev., 2012, 112, 724. 3 X. Xu, J. Wang and Y. Long, Sensors, 2006, 6, 1751. 4 M. Xue, L. Fan, Z. Kang, W. Zhang, H. Li and S. Qiu, J. Mater. Chem., 2012, 22, 17644. 5 L. E. Kreno, K. Leong, O. K. Farha, M. Allendorf, R. P. Van Duyne and J. T. Hupp, Chem. Rev., 2011, 112, 1105. 6 H.-L. Jiang, T. Akita, T. Ishida, M. Haruta and Q. Xu, J. Am. Chem. Soc., 2011, 133, 1304. 7 A. K. Cheetham, G. Ferey and T. Loiseau, Angew. Chem., Int. Ed., 1999, 38, 3268. 8 M. E. Davis, Nature, 2002, 417, 813. 9 A. Schneemann, V. Bon, I. Schwedler, I. Senkovska, S. Kaskel and R. A. Fischer, Chem. Soc. Rev., 2014, 43, 6062. 10 X. Tang, J. Provenzano, Z. Xu, J. Dong, H. Duan and H. Xiao, J. Mater. Chem., 2011, 21, 181. 11 Supramolecular Photochemistry: Controlling  Photochemical Processes, ed. V. Ramamurthy and Y. Inoue, Wiley, 2011. 12 H. Kobayashi, T. Ueda, K. Miyakubo, J. Toyoda, T. Eguchi and A. Tani, J. Mater. Chem., 2005, 15, 872.13 H. Kobayashi, T. Ueda, K. Miyakubo, T. Eguchi and A. Tani, Bull. Chem. Soc. Jpn., 2007, 80, 711. 14 H. Kobayashi, T. Ueda, K. Miyakubo, T. Eguchi and A. Tani, Mol. Cryst. Liq. Cryst., 2009, 506, 150. 15 H. Kobayashi, T. Asaji and A. Tani, Materials, 2010, 3, 3625. 16 P. J. Langley, J. M. Rawson, J. N. B. Smith, M. Schuler, R. Bachmann, A. Schweiger, F. Palacio, G. Antorrena, G. Gescheidt, A. Quintel, P. Rechsteiner and J. Hulliger, J. Mater. Chem., 1999, 9, 1431.  17 H. I. Süss, T. Wuest, A. Sieber, R. Althaus, F. Budde, H.-P. Lüthi, G. D. McManus, J. M. Rawson and J. Hulliger, CrystEngComm, 2002, 4, 432. 18 T. B. Faust and D.M. D'Alessandro, RSC Adv., 2014, 4, 17498. 19 S. V. Potts, L.J. Barbour, D. A. Haynes, J. M. Rawson and G. O. Lloyd, J. Am. Chem. Soc. 2011, 133, 12948. 20 H. J. Cowley, J. J. Hayward, D. R. Pratt and J. M. Rawson, Dalton Trans., 2014, 43, 1332. 21 L. Dobrzańska, G. O. Lloyd, H. G. Raubenheimer, L. J. Barbour, J. Am. Chem. Soc., 2006, 128, 698; A. Heyns,2012, PhD thesis, Stellenbosch University; V. I. Nikolayenko, A. Heyns and L. J. Barbour, manuscript in preparation. 22 H. Wahl, T. Le Roux and D. A. Haynes, 2017, Cryst. Gowth Des. DOI 10.1021/acs.cgd.7b00684. 23 L. Yang, D. R. Powell and R. P. Houser, Dalton Trans., 2007, 955-964.24 A. Winter, K. Thiel, A. Zabel, T. Klamroth, A. Pöppl, A. Kelling, U. Schilde, A. Taubert and P. Strauch, New. J. Chem., 2014,38, 1019.

Chemical Communications

Inclusion of a dithiadiazolyl radical in a seemingly non-porous solid

Incorporation of a dithiadiazolyl radical into a dynamic paramagnetic metallocycle yields an unusual paramagnetic hybrid material with exchange coupling between host and guest.</p

Varvara I. Nikolayenko

Leonard J. Barbour

Ana Arauzo

Javier Campo

Jeremy M. Rawson

Delia A. Haynes

Crossref

Scholarship at UWindsor

University of Windsor Scholarship at UWindsor Chemistry and Biochemistry Publications Department of Chemistry and Biochemistry 9-2017 Inclusion of a dithiadiazolyl radical in a seemingly non-porous solid Varvara I. Nikolayenko, Stellenbosch University Leonard J. Barbour Stellenbosch University Ana Arauzo University of Zaragoza Javier Campo University of Zaragoza Jeremy M. Rawson University of Windsor See next page for additional authors Follow this and additional works at: https://scholar.uwindsor.ca/chemistrybiochemistrypub  Part of the Biochemistry, Biophysics, and Structural Biology Commons, and the Chemistry Commons Recommended Citation Nikolayenko,, Varvara I.; Barbour, Leonard J.; Arauzo, Ana; Campo, Javier; Rawson, Jeremy M.; and Haynes, Delia A.. (2017). Inclusion of a dithiadiazolyl radical in a seemingly non-porous solid. Chemical Communications (82), 11310-11313. https://scholar.uwindsor.ca/chemistrybiochemistrypub/92 This Article is brought to you for free and open access by the Department of Chemistry and Biochemistry at Scholarship at UWindsor. It has been accepted for inclusion in Chemistry and Biochemistry Publications by an authorized administrator of Scholarship at UWindsor. For more information, please contact scholarship@uwindsor.ca. Authors Varvara I. Nikolayenko,; Leonard J. Barbour; Ana Arauzo; Javier Campo; Jeremy M. Rawson; and Delia A. Haynes This article is available at Scholarship at UWindsor: https://scholar.uwindsor.ca/chemistrybiochemistrypub/92 Published as: Chem Comm, 2017, 53, 11310 - 11313 COMMUNICATION This journal is © The Royal Society of Chemistry 20xx J. Name., 2013, 00, 1-3 | 1Please do not adjust margins Please do not adjust margins Received 00th January 20xx, Accepted 00th January 20xx DOI: 10.1039/x0xx00000x www.rsc.org/ Inclusion of a dithiadiazolyl radical in a seemingly non-porous solid Varvara I. Nikolayenko,a Leonard J. Barbour,a Ana Arauzo,b Javier Campo,b Jeremy M. Rawsonc and Delia A. Haynes*a Inclusion of the dithiadiazolyl radical PhCNSSN• into the dynamically porous metallocycle [Cu2(L1)2Cl4], where L1 is the bidentate ligand 1,3-bis(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene, has been achieved by gas phase diffusion. Single crystal X-ray diffraction, powder X-ray diffraction, UV-visible spectroscopy, EPR and SQUID magnetometry studies confirm inclusion of the radical into this seemingly non-porous material, and illustrate the presence of antiferromagnetic coupling between the paramagnetic host and guest species. The radical guest is readily released by heating or by the addition of solvent (CH2Cl2). The evolution and exploitation of host–guest interactions for use in gas sequestration and storage,1,2 chemical sensing,3-5 and heterogeneous catalysis6-8 have garnered considerable interest in recent years owing to the rapid expansion of the number of known dynamically porous solid-state materials.9 As this field of chemistry becomes more established, researchers are focussing on property development, including magnetic behaviour, light modulation, spin-state bistability, electron, hole and ion mobility, ferroelectricity and luminescence. Each of the aforementioned properties is governed by host–guest interactions: sensors require one entity to impose some measurable change on the other, for example,10 while orientation-specific binding can lead to regio- and/or enantioselective transformations in catalysis.11 The inclusion of radical guest molecules into porous materials such as hydrogen-bonded frameworks (HOFs), metal-organic frameworks (MOFs) or discrete cavities (such as those found in metallocycles) offers the potential for strong host-guest and guest-guest electronic interactions, potentially resulting in interesting magnetic or transport properties. The majority of known HOF-radical inclusion compounds were obtained by co-crystallisation of the guest with an organic host from solution or the gas phase.12-17 A recent review by D'Alessandro et al. illustrates the increase in reports of MOFs containing radical moieties, either incorporated into the host backbone or as encapsulated guests.18 However, the number of reported inclusion compounds containing paramagnetic guests still remains low. In fact, there are only two reports of the inclusion of thiazyl radicals into metal-containing frameworks, both arising from our groups, and both involving diamagnetic host frameworks. One study reports the inclusion of benzodithiazolyl and methylbenzodithiazolyl into MIL-53(Al),19 while the other reports the inclusion of PhCNSSN• into Faujasite.20 Notably, in the former complex the walls of the host cavity rotate to accommodate the guest, indicating a responsive relationship between the host and the guest. Previous studies in the Barbour group21 have shown the copper metallocycle [Cu2(L1)2Cl4] (Scheme 1, hereafter 1a) to be a dynamic material, capable of undergoing multiple single crystal-to-single crystal (SC-SC) guest-inclusion reactions. A variety of guests have been included in the metallocyclic host, yielding host-guest systems 1-11, where the host adapts the size of the cavity to best suit a particular guest via rotation of the imidazole rings.21 Since 1a is a highly stable, dynamic host that is inherently paramagnetic, we decided to investigate inclusion of a thiazyl radical (4-phenyl-1,2,3,5-dithiadiazolyl, PhCNSSN•, Scheme 1) into this material, with the aim of inducing communication between the spin on the host and the spin on the guest. Since guest encapsulation is accompanied by cooperative motion of the host, inducing a highly specific change in the solvent-accessible space and in turn in the chemical environment of the metal, single-crystal (SC) X-ray data in conjunction with variable temperature solid-state EPR were employed to obtain a clearer understanding of the host-guest interaction. a. Department of Chemistry and Polymer Science, Stellenbosch University, P. Bag X1 Matieland, 7602, Stellenbosch, South Africa. E-mail: dhaynes@sun.ac.za. b. Aragón Materials Science Institute (CSIC-University of Zaragoza) and CondensedMatter Physics Dept. Facultad de Ciencias, 50009 Zaragoza (Spain) c. Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor, ON, Canada N9B 3P4 Electronic Supplementary Information (ESI) available: [Full experimental details,synthesis, TGA, DSC, EPR SQUID and DFT; CCDC deposition numbers 1566860-1566863 ]. See DOI: 10.1039/x0xx00000x COMMUNICATION Journal Name 2 | J. Name., 2012, 00, 1-3 This journal is © The Royal Society of Chemistry 20xx Please do not adjust margins Please do not adjust margins The host was prepared as its methanol solvate 1, following the previously reported synthesis,21 and was activated by heating under dynamic vacuum at 100 °C for 24 hours to eliminate the included methanol, yielding the apohost 1a. Bulk phase purity was established using powder X-ray diffraction (Figure S2). Previous work conducted by Barbour, Haynes and co-workers has shown that materials that are solid but sufficiently volatile at room temperature can be included into framework hosts by sorption of the guest directly from the gas phase.19,21,22 This is also possible for metallocycles such as 1a.21 The volatility of PhCNSSN• permitted its inclusion into the apohost 1a when the two species were heated together in vacuo at 80 °C. (Figure S1). After 24 hours of exposure to vapours of the radical, crystals of 1a had undergone a distinct colour change from green to deep red (almost black), 12 (Figure 1). The UV absorption spectra of the two samples (Figure S9) confirm the observed colour change, with 1a absorbing the majority of the visible spectrum except in the green region, while 12 does not transmit any light. The powder pattern of bulk 12 is similar to that of 1a (Figure S3), albeit with some small differences in peak positions/intensities, indicating that the radical has been included in the host without significant structural changes to the crystal structure. Notably there is no evidence for neat PhCNSSN• in the PXRD, confirming that the observed colour change is not as a result of crystallisation of the radical on the surface of the host crystals. The structure of 12 was elucidated by means of single-crystal X-ray diffraction, as inclusion of the radical is a SC-SC process (Table S1). The structure shows that the space group of the host (P21/c) is maintained in 12, but there is an increase in the length of the b axis, with a corresponding increase in the unit cell volume. In addition to the metal, ligand and chloride counterions present in the asymmetric unit of 1a, the asymmetric unit of 12 also contains one dithiadiazolyl radical, which is disordered across an inversion centre with a site occupancy of ca. 30%, resulting in a guest occupancy of ca. 60%. Closer examination of the two crystal structures determined at 100 K (Figure 1) shows notable diﬀerences in the Cu―Cu distances, as well in the phenyl(centroid)―phenyl(centroid) and imidazole(centroid)―imidazole(centroid) distances. In order to accommodate the radical guest, the copper metallocycle expands along the shorter dimension (Cu-Cu), while contracting along the longer dimension (phenyl-phenyl). In 12, one of the two imidazole moieties is disordered over two positions with the minor fragment having a site occupancy of 30%. This disorder is attributed to weak hydrogen bonding between the nitrogen atom of the radical guest and the hydrogen atom of the host imidazole. Extension of the ASU shows the radicals encapsulated within stacks of metallocycles (Figure 2). Guest inclusion results in two cavities within the host merging, analogous to the behaviour of the host on inclusion of naphthalene.21 Merged cavities are separated from one another because the radical guest is too large to be included between every metallocycle pair. however, the Cu…Cu distances between metallocycles remain constant along the metallocycle stack (Fig. 2b). The distortion of the host lattice is manifested in a subtle change in the coordination geometry at the four-coordinate copper(II) centre. For the host complex, the τ4 parameter (defined as [360 – (α + β)]/141 where α and β are the two largest angles subtended at Cu) is 0.37, intermediate between square-planar (τ4 = 0) and tetrahedral (τ4 = 1) geometries. In 12 the geometry at Cu is slightly more compressed towards square planar (τ4 = 0.32). No degradation of 12 was noted using PXRD or EPR, even when samples had been exposed to air in ambient conditions for extended periods of time (Figure S4). This enhanced stability of the radical within the metallocycle is in stark contrast to the pure radical, which degrades when not kept under an inert atmosphere. In addition, TGA data show no significant mass loss for 12 up to 100 oC (Figure S5). These findings are consistent Journal Name  COMMUNICATION This journal is © The Royal Society of Chemistry 20xx J. Name., 2013, 00, 1-3 | 3Please do not adjust margins Please do not adjust margins with previous studies, where thiazyl radicals included in porous materials were shown to be stable for up to a month.19 Solid-state EPR spectroscopy was used to further probe the structures of both 1a and the new radical-containing paramagnetic hybrid material 12. Both 1a and 12 yield essentially axial spectra with a small rhombic distortion (Fig. 3, ESI). Previous EPR studies on distorted CuCl42- anions (0.72 > τ4 > 0.61; where τ4 is defined as [360 – (α + β)]/141 where α andβ are the two largest angles subtended at Cu23) producerhombic spectra with g|| > g⊥ with increasing distortionstowards square planar, leading to a reduction in the magnitudeof the g-tensor.24 In this context it is notable that both 1a and12 also exhibit g|| > g⊥, with smaller g-values for 12, which iscloser to square planar. The average g-values for 1a and 12 (2.12and 2.11, respectively) are smaller than those for CuCl42-,consistent with geometries significantly closer to square planar(τ4 = 0.37 and 0.32). Notably the EPR spectrum of 12 does notexhibit an observable component associated with the PhCNSSNradical (g = 2.01).The EPR linewidth of the radical inclusion complex is substantially greater than that of the host framework, which can be attributed to dipolar broadening between radical and host, or through some exchange interaction, such that the radical no longer behaves as an isolated S = ½ spin system. The presence of the radical in the host framework was confirmed by displacement of the guest by addition of CH2Cl2 (Fig. 3c). To examine the nature of the host-guest interaction, variable temperature dc SQUID magnetometry measurements were made on 1a and 12. The parent host framework was found to exhibit Curie-Weiss paramagnetism across the range 1.8 – 300 K with C = 0.842 emu K mol-1 and θ = -2.0 K, consistent with very weak antiferromagnetic interactions between two S = ½ ions with g = 2.12, in agreement with the value determined by EPR spectroscopy (2.12). M vs H studies at 1.8 and 10 K are nicely replicated with two S = ½ ions using g = 2.12 and a mean field correction term to take into account weak anti-ferromagnetic interactions (θ = -0.95 K, see ESI). Radical inclusion leads to a marked change in the paramagnetism of the sample. Down to 50 K the magnetism once again follows Curie-Weiss behaviour but the Curie constant is a little larger (C = 0.954 emu K mol-1), consistent with an increase in the total number of spin centres in the sample. The Curie constant equates to 24% S = ½ (based on TGA data on the same sample recorded after the SQUID measurements) with g = 2.0 and two S = ½ Cu2+ centres with g = 2.15. The Weiss constant (θ = -5.7 K), reflects weak antiferromagnetic interactions which could comprise both host-host and host-guest interactions. A subtle change in gradient is observed below 20 K (C = 0.772 emu K mol-1, θ = -0.63 K), consistent with antiferromagnetic coupling between host Cu2+ ions and the guest PhCNSSN radicals. This interpretation is supported by DFT calculations (see ESI), which reveal exchange couplings between the radical and Cu2+ of -11 and -12 cm-1 for the two copper atoms in the metallocycle. In conclusion, the incorporation of a dithiadiazolyl radical into the dynamic paramagnetic metallocycle 1a results in an unusual paramagnetic hybrid material, 12, in which SQUID and DFT studies support the presence of exchange coupling between host and guest. The stability of the radical is significantly enhanced by inclusion in the metallocyclic host. There are no conflicts of interest to declare. We thank the National Research Foundation of South Africa and Stellenbosch University for funding. J.M.R. acknowledges the support of the Canada Research Chair Program. J.C. acknowledges the Grant No. MAT2015-68200- C2-2-P from the Spanish Ministry of Economy and Competitiveness. Fig. 4 Temperature dependence of χT for 1a (blue circles) and 12 (purple circles). The inset is an expansion of the data between 0 and 50 K.0.00.20.40.60.81.00 100 200 300χT (emu.K.mol-1)Temperature (K)121a121ab) 12 a) 1a c)COMMUNICATION Journal Name 4 | J. Name., 2012, 00, 1-3 This journal is © The Royal Society of Chemistry 20xx Please do not adjust margins Please do not adjust margins Notes and references 1 H. Wu, W. Zhou and T. Yildirim, J. Am. Chem. Soc., 2007,129, 5314. 2 K. Sumida, D. L. Rogow, J. A. Mason, T. M. McDonald., D. Bloch, Z. R. Herm, T.-H. Bae and J. R. Long, Chem. Rev., 2012, 112, 724. 3 X. Xu, J. Wang and Y. Long, Sensors, 2006, 6, 1751. 4 M. Xue, L. Fan, Z. Kang, W. Zhang, H. Li and S. 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Inclusion of a dithiadiazolyl radical in a seemingly non-porous solid

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