148103-20-2Relevant academic research and scientific papers
Formation of a Polythreaded, Metal–Organic Framework Utilizing an Interlocked Hexadentate, Carboxylate Linker
Gholami, Ghazale,Zhu, Kelong,Ward, Jas S.,Kruger, Paul E.,Loeb, Stephen J.
, p. 4524 - 4529 (2016)
A unique hexacarboxylate linker was prepared on the basis of an interlocked [2]rotaxane motif. The linker contains four carboxylate groups attached to a rigid, H-shaped axle and two carboxylate units appended to a crown ether wheel. The resulting ZnII-based metal–organic framework material has a unique lattice, in which three independent 3-periodic frameworks (threefold interpenetration) are interconnected only by virtue of the threading of their individual components in the rotaxane linker.
Efficient syntheses of novel cryptands based on bis(m-phenylene)-26-crown-8 and their complexation with paraquat
Xu, Zhikai,Huang, Xinmin,Liang, Jidong,Zhang, Suhui,Zhou, Songgen,Chen, Mujuan,Tang, Mingfei,Jiang, Lasheng
, p. 1904 - 1911 (2010)
High-yielding syntheses of two novel cryptands based on bis(m-phenylene)-26-crown-8 are reported. One-step [2+2] cyclization of methyl 3,5-dihydroxybenzoate with tri(ethylene glycol) ditosylate under pseudo-high-dilution conditions gave BMP26C8 (1) in 28% yield. Reduction of 1 with LAH, followed by deprotonation (NaH) and alkylation with propargyl bromide, afforded the dialkynated BMP26C8 (3) in high yield (two-step 84%). Unimolecular macrocyclization of 3 through copper(II) -mediated Eglinton coupling generated the diacetylene-containing cryptand 4 in 97 % yield. Pd/Ccatalyzed hydrogenation of 4 yielded the cryptand 5 (93 %). Their structures were confirmed by NMR, ESI-MS, and Xray analysis. The complexation behavior of these new cryptands with paraquat was also studied, and it was found that these cryptands bind paraquat more strongly than the corresponding BMP26C8. The association constants (K 1 and K2) in acetone solution were determined to be K 1 = 914 M-1, K2 = 229 M-1 for complex 42-6 and K1 = 758 M-1, K2 = 190 M-1 for complex 52,6. Moreover, the two new [3]pseudorotaxane-like complexes 42,6 and 52,6 were also obtained in the solid state, as confirmed by X-ray analysis.
Selectivity algorithm for the formation of two cryptand/paraquat catenanes
Liu, Ming,Li, Shijun,Hu, Menglong,Wang, Feng,Huang, Feihe
supporting information; scheme or table, p. 760 - 763 (2010/04/06)
(Figure Presented) Two [2]catenanes based on two different cryptand hosts, a dibenzo-24-crown-8-based cryptand and a bis(m-phenylene)-26-crown-8-based cryptand, have been synthesized and characterized. These two cryptand hosts only have a minor difference in chemical structure. However, this minor structural difference leads to big differences in the configurations and packing modes of the resulting catenanes. In addition, from the crystal structures of the two catenanes, we found that the cyclophane guest seems to have a selectivity algorithm and chooses the larger-size rings to go through and interlock with.
Structural control of co-receptor binding in porphyrin-bipyridinium supramolecular assemblies
Gunter, Maxwell J.,Jeynes, Tyrone P.,Johnston, Martin R.,Turner, Peter,Chen, Zhangping
, p. 1945 - 1957 (2007/10/03)
A new series of porphyrin-based receptors for the bipyridinium ions paraquat and diquat, consisting in each case of a porphyrin with an over-arching dibenzo-crown ether, and related structures with hydroquinol-containing polyether straps is described. In all cases, the appended superstructure is connected to the porphyrin via ether linkages from the o-positions of the meso-aryls of the octaalkyl-5,15-diaryl substituted porphyrins. Solution studies of the complexes are compared to those of a previously reported set of related structures with amide linkages in place of the ethers and, at variance with the amide series, reveal conformations in which the complexed bipyridinium is parallel to the porphyrin sub-unit rather than perpendicular. Binding constants for all of the free-base and zinc porphyrin derivatives with both paraquat and diquat in various solvents allow the following principles to be established: (i) the binding strength decreases with increasing solvent polarity, (ii) there is little difference in the binding strength between the free base and zinc derivatives for a given receptor, (iii) binding is stronger for the more constrained 4(i) compared to the looser 4(ii), (iv) in general, paraquat binds more strongly than diquat, (v) the single-strapped analogues 6 are relatively ineffective as receptors for these bipyridinium guests, (vi) for a given sized dibenzo-crown ether cap or polyether strap, the substitution of ether linkages for the amide linkages in the related family of receptors 1 results in stronger binding. A similar binding motif is described for a naphthoquinol-strapped porphyrin 5. The solution studies are supported by X-ray crystal structures of two of the paraquat complexes which indicate that the guest is held by face-to-face π-π interactions with the porphyrin, by C-H ... O hydrogen bonds, by electrostatic forces, and by either face-to-face π-stacking with the hydroquinol unit or by edge-to-face interactions in the case of the dibenzo-crown strapped molecule.
Porphyrin-Crown Ether Macrotricyclic Co-receptors for Bipyridinium Cations
Gunter, Maxwell J.,Johnston, Martin R.
, p. 995 - 1008 (2007/10/02)
In order to employ non-covalent interactions to position methyl viologen close to a photoactive centre (in this case a porphyrin) a dibenzo-crown ether, containing meta-substituted aromatic rings and tetraethylene glycol ether chains, was strapped across a porphyrin to produce a macrotricyclic host.This host was observed to complex methyl viologen (paraquat) (Ka 50 and 250 dm3 mol-1 and ΔG0 -2.3 and -2.9 kcal mol-1 at 298 K, respectively) and (PF6)2 (Ka 1350 dm3 mol-1, ΔG -4.3 kcal mol-1 at 298 K) by an induced fit mechanism, as a result of rotational barriers associated with the diaryl amide linkage.Efforts to improve the complexing ability of these types of hosts involved a shortening of the linking ether chains and reduction of the amide group linking the crown ether and porphyrin moieties.Of these two directions the reduced host was most successful, complexing all the bipyridinium dications examined, although ligand exchange reactions complicated the binding of the platinum complex (for paraquat Ka 480 dm3 mol-1, ΔG0 -3.6 kcal mol-1 at 298 K; for diquat Ka 80 dm3 mol-1, ΔG -2.6 kcal mol-1 at 298 K).In contrast, the host containing shortened ether chains was observed to have similar complexing abilities to its predecessor, as a result of comparable solution conformations (for paraquat Ka 50 dm3 mol-1, ΔG0 -2.3 kcal mol-1 at 298 K; for (PF6)2 Ka 365 dm3 mol-1, ΔG0 -2.9 kcal mol-1 at 298 K).However, in this case binding by the platinum complex within the constricted cavity of the host resulted in deformation of the porphyrin and an increased activation barrier to complexation.
