I19-Small Molecule Single Crystal Diffraction
|
Diamond Proposal Number(s):
[15848]
Open Access
Abstract: Molecular crystals can be bent elastically by expansion or plastically by delamination into slabs that glide along slip planes. Here we report that upon bending, terephthalic acid crystals can undergo a mechanically induced phase transition without delamination and their overall crystal integrity is retained. Such plastically bent crystals act as bimorphs and their phase uniformity can be recovered thermally by taking the crystal over the phase transition temperature. This recovers the original straight shape and the crystal can be bent by a reverse thermal treatment, resulting in shape memory effects akin of those observed with some metal alloys and polymers. We anticipate that similar memory and restorative effects are common for other molecular crystals having metastable polymorphs. The results demonstrate the advantage of using intermolecular interactions to accomplish mechanically adaptive properties with organic solids that bridge the gap between mesophasic and inorganic materials in the materials property space.
|
Aug 2019
|
|
I19-Small Molecule Single Crystal Diffraction
|
Diamond Proposal Number(s):
[17379]
Abstract: We report a family of hybrid [2]rotaxanes based on inorganic [Cr7NiF8(O2CtBu)16]- (“{Cr7Ni}”) rings templated about organic threads that are terminated at one end with pyridyl groups. These rotaxanes can be coordinated to [Cu(hfac)2] (where hfac = 1,1,1,5,5,5-hexafluoroacetylacetone), to give 1:1 or 1:2 Cu:{Cr7Ni} adducts: {[Cu(hfac)2](py-CH2NH2CH2CH2Ph)[Cr7NiF8(O2CtBu)16]}, {[Cu(hfac)2][py-CH2NH2CH2CH3][Cr7NiF8(O2CtBu)16]}, {[Cu(hfac)2]([py-CH2CH2NH2CH2C6H4SCH3][Cr7NiF8(O2CtBu)16])2}, {[Cu(hfac)2]([py-C6H4-CH2NH2(CH2)4Ph][Cr7NiF8(O2CtBu)16])2}, and {[Cu(hfac)2]([3-py-CH2CH2NH2(CH2)3SCH3][Cr7NiF8(O2CtBu)16])2}, the structures of which have been determined by X-ray diffraction. The {Cr7Ni} rings and CuII ions both have electronic spin S = ½, but with very different g-values. Continuous-wave EPR spectroscopy reveals the exchange interactions between these dissimilar spins, and hence the communication between the different molecular components that comprise these supramolecular systems. The interactions are weak such that we observe AX or AX2 type spectra. The connectivity between the {Cr7Ni} ring and thread terminus is varied such that the magnitude of the exchange interaction J can be tuned. The coupling is shown to be dominated by through-bond rather than through-space mechanisms.
|
Aug 2019
|
|
I11-High Resolution Powder Diffraction
I19-Small Molecule Single Crystal Diffraction
|
Abstract: A new porous and flexible metal-organic framework (MOF) has been synthesised from the flexible asymmetric linker N-(4-Carboxyphenyl)succinamate (CSA) and heptanuclear zinc oxo-clusters of formula [Zn7O2(Carboxylate)10DMF2] involving two coordinated terminal DMF ligands. The structural response of this MOF to the removal or exchange of its guest molecules has been probed using a combination of experimental and computational approaches. The topology of the material, involving double linker connections in the a and b directions and single linker connections along the c axis, is shown to be key in the materials anisotropic response. The a and b directions remain locked during guest removal, while the c axis linker undergoes large changes significantly reducing the material’s void space. The changes to the c axis linker involve a combination of a hinge motion on the linker’s rigid side and conformational rearrangements on its flexible end, which were probed in detail during this process despite the presence of crystallographic disorder along this axis which prevented accurate characterisation by experimental methods alone. While inactive during guest removal, the flexible ends of the a and b axis linkers are observed to play a prominent role during DMF to DMSO solvent exchange, facilitating the exchange reaction arising in the cluster.
|
Aug 2019
|
|
I19-Small Molecule Single Crystal Diffraction
|
Jesus
Ferrando-soria
,
Antonio
Fernandez
,
Deepak
Asthana
,
Selina
Nawaz
,
Iñigo J.
Vitorica-yrezabal
,
George F. S.
Whitehead
,
Christopher A.
Muryn
,
Floriana
Tuna
,
Grigore A.
Timco
,
Neil D.
Burton
,
Richard E. P.
Winpenny
Open Access
Abstract: Molecules that are the size of small proteins are difficult to make. The most frequently examined route is via self-assembly, and one particular approach involves molecular nanocapsules, where ligands are designed that will enforce the formation of specific polyhedra of metals within the core of the structure. Here we show that this approach can be combined with mechanically interlocking molecules to produce nanocapsules that are decorated on their exterior. This could be a general route to very large molecules, and is exemplified here by the synthesis and structural characterization of a [13]rotaxane, containing 150 metal centres. Small angle X-ray scattering combined with atomistic molecular dynamics simulations demonstrate the compound is intact in solution.
|
Aug 2019
|
|
I19-Small Molecule Single Crystal Diffraction
|
Diamond Proposal Number(s):
[15768]
Abstract: The systematic assembly of supramolecular arrangements is a persistent challenge in modern coordination chemistry, especially where further aspects of complexity are concerned, as in the case of large molecular mixed‐metal arrangements. One targeted approach to such heterometallic complexes is to engineer metal‐based donor ligands of the correct geometry to build 3‐D arrangements upon coordination to other metals. This simple idea has, however, only rarely been applied to main group metal‐based ligand systems. Here we show that the new, bench‐stable tris(3‐pyridyl)stannane ligand PhSn(3‐Py)3 (3‐Py = 3‐pyridyl) provides simple access to a range of heterometallic Sn(IV)/transition metal complexes, and that the presence of weakly coordinating counteranions can be used to build discrete molecular arrangements involving anion encapsulation. This work therefore provides a building strategy in this area, which parallels that of supramolecular transition metal chemistry.
|
Aug 2019
|
|
I19-Small Molecule Single Crystal Diffraction
|
Wei
Zhang
,
Yong
Hua
,
Linqin
Wang
,
Biaobiao
Zhang
,
Yuanyuan
Liu
,
Peng
Liu
,
Valentina
Leandri
,
Yu
Guo
,
Hong
Chen
,
James M.
Gardner
,
Licheng
Sun
,
Lars
Kloo
Diamond Proposal Number(s):
[15819, 20805]
Abstract: Two zinc-based coordination complexes Y3 and Y4 have been synthesized, characterized and their performance as hole-transport materials (HTMs) for perovskite solar cells (PSCs) have been investigated. The complex Y3 contains two separate ligands, and the molecular structure can be seen as a dis-connected porphyrin ring. On the other hand, Y4 consists of a porphyrin core, and therefore a more extended conjugated system as compared to Y3. The optical and redox properties of the two different molecular complexes are comparable. However, the hole-mobility and conductivity of Y4 as macroscopic material are remarkably higher than that of Y3. Furthermore, when employed as hole-transport materials in perovskite solar cells, cells containing Y4 show a power conversion efficiency (PCE) of 16.05%, comparable to the Spiro-OMeTAD based solar cells with an efficiency around 17.08%. In contrast, solar cells based on Y3 show a negligible efficiency of about 0.01%. The difference in performance of Y3 and Y4 are analyzed and can be attributed to the difference in packing of the non-planar and planar building blocks in the corresponding materials.
|
Aug 2019
|
|
I19-Small Molecule Single Crystal Diffraction
|
Diamond Proposal Number(s):
[11397]
Open Access
Abstract: Porphyrin‐hexabenzocoronene architectures serve as good model compounds to study light harvesting systems. Herein, the synthesis of porphyrin functionalized hexa‐peri‐hexa‐benzocoronenes (HBCs), in which one or more porphyrins are covalently linked to a central HBC core, is presented. Therefore, a series of hexaphenylbenzenes (HPBs) was prepared and reacted under oxidative Scholl conditions. The transformation to the respective HBC derivatives worked well with mono‐ and tri‐porphyrin substituted HPBs. However, if more porphyrins are attached to the HPB core, Scholl oxidations are hampered or completely suppressed. Hence, a change of the synthetic strategy was necessary to first pre‐forming the HBC core, followed by the introduction of the porphyrins. All products were fully characterized, including, if possible, single crystal XRD. UV/Vis absorption spectra of porphyrin‐HBCs showed, depending on the number of porphyrins as well as with respect to the substitution pattern, variations in their spectral features with strong distortions of the porphyrins’ B‐band.
|
Aug 2019
|
|
I19-Small Molecule Single Crystal Diffraction
|
Diamond Proposal Number(s):
[15762]
Open Access
Abstract: Traditionally small-molecule crystallographers have not usually observed or recognized significant radiation damage to their samples during diffraction experiments. However, the increased flux densities provided by third-generation synchrotrons have resulted in increasing numbers of observations of this phenomenon. The diversity of types of small-molecule systems means it is not yet possible to propose a general mechanism for their radiation-induced sample decay, however characterization of the effects will permit attempts to understand and mitigate it. Here, systematic experiments are reported on the effects that sample temperature and beam attenuation have on radiation damage progression, allowing qualitative and quantitative assessment of their impact on crystals of a small-molecule test sample. To allow inter-comparison of different measurements, radiation-damage metrics (diffraction-intensity decline, resolution fall-off, scaling B-factor increase) are plotted against the absorbed dose. For ease-of-dose calculations, the software developed for protein crystallography, RADDOSE-3D, has been modified for use in small-molecule crystallography. It is intended that these initial experiments will assist in establishing protocols for small-molecule crystallographers to optimize the diffraction signal from their samples prior to the onset of the deleterious effects of radiation damage.
|
Jul 2019
|
|
I19-Small Molecule Single Crystal Diffraction
|
Diamond Proposal Number(s):
[15768]
Abstract: Controlled directional transport of molecules is essential to complex natural systems, exemplified by cellular transport up to organismal circulatory systems. In contrast to these natural systems, synthetic systems that enable transport of molecules between several spatial locations on the macroscopic scale, when external stimuli are applied, remain to be explored. Here we report the transfer of a supramolecular cage with controlled directionality between three phases, based on the cage that responds reversibly in two distinct ways to different anions. Notably, circulatory phase transfer of the cage was demonstrated based on a system where the three layers of solvent are arranged within a circular track. The direction of circulation between solvent phases depended upon the order of addition of anions.
|
Jul 2019
|
|
I19-Small Molecule Single Crystal Diffraction
|
Diamond Proposal Number(s):
[15768]
Abstract: Here we describe the formation of a trigonal prismatic cage, utilizing 2-formyl-1,8-naphthyridine subcomponents to bind pairs of silver(I) ions in close proximity. This cage is the first example of a new class of subcomponent self-assembled polyhedral structures having bimetallic vertices, as opposed to the single metal centers that typically serve as structural elements within such cages. Our new cage self-assembles around a pair of anionic templates, which are shown by crystallographic and solution-phase data to bind within the central cavity of the structure. Many different anions serve as competent templates and guests. Elongated dianions, such as the strong oxidizing agent peroxysulfate, also serve to template and bind within the cavity of the prism. The principle of using subcomponents that have more than one spatially close, but nonchelating, binding site may thus allow access to other higher-order structures with multimetallic vertices.
|
Jul 2019
|
|