Showing papers by "Alexander J. Blake published in 2019"

Host–guest selectivity in a series of isoreticular metal–organic frameworks: observation of acetylene-to-alkyne and carbon dioxide-to-amide interactions

Abstract: In order to develop new porous materials for applications in gas separations such as natural gas upgrading, landfill gas processing and acetylene purification it is vital to gain understanding of host-substrate interactions at a molecular level. Herein we report a series of six isoreticular metal-organic frameworks (MOFs) for selective gas adsorption. These materials do not incorporate open metal sites and thus provide an excellent platform to investigate the effect of the incorporation of ligand functionality via amide and alkyne groups on substrate binding. By reducing the linker length of our previously reported MFM-136, we report much improved CO2/CH4 (50:50) and CO2/N¬2 (15:85) selectivity values of 20.2 and 65.4, respectively (1 bar and 273 K), in the new amide-decorated MOF, MFM-126. The CO2 separation performance of MFM-126 has been confirmed by dynamic breakthrough experiments. In situ inelastic neutron scattering and synchrotron FT-IR microspectroscopy were employed to elucidate dynamic interactions of adsorbed CO2 molecules within MFM-126. Upon changing the functionality to an alkyne group in MFM-127, the CO2 uptake decreases but the C2H2 uptake increases by 68%, leading to excellent C2H2/CO2 and C2H2/CH4 selectivities of 3.7 and 21.2, respectively. Neutron powder diffraction enabled the direct observation of the preferred binding domains in MFM-126 and MFM-127, and, to the best of our knowledge, we report the first example of acetylene binding to an alkyne moiety in a porous material, with over 50% of the acetylene observed within MFM-127 displaying interactions (<4 A) with the alkyne functionality of the framework.

Unequivocal Experimental Evidence of the Relationship between Emission Energies and Aurophilic Interactions.

Abstract: In this paper, we describe experimental evidence of a change in the emission energy as a function of the Au–Au distance. We have employed a luminescent complex exhibiting an aurophilic interaction,...

[9]aneN3-based fluorescent receptors for metal ion sensing, featuring urea and amide functional groups.

Abstract: We describe here the synthesis and coordination properties of three new derivatives of [9]aneN3 containing phenyl/quinoline pendant arm derivatives (L1, L2 and L3, respectively) also featuring urea (L1–L2) or amide (L3) functions as “non-innocent” spacers. At first, L1, L2 and L3 were studied considering the interaction with a series of anions (AcO−, BzO−, H2PO4−, F−, and Cl−) by means of 1H NMR measurements. Subsequently, the optical responses of L2 and L3 in the presence of several metal ions Cd2+, Co2+, Cu2+, Fe3+, Hg2+, K+, Mg2+, Mn2+, Ni2+, Zn2+ and Pb2 were analysed in MeCN/H2O (4 : 1 v/v). As observed by spectrophotometric and spectrofluorimetric titrations, there were significant changes in the absorbance and fluorescent emission of L2 upon addition of increasing amounts of Cd2+, Zn2+, Pb2+ and Cu2+ in MeCN/H2O (4 : 1 v/v). In particular, titrations of L2 with Cd2+, Zn2+ or Pb2+ showed an almost comparable CHEF effect up to an M2+/L2 molar ratio of 1. Overall, no significant optical selectivity was observed in the case of L2. Conversely, L3 revealed an OFF–ON selective response only in the presence of the Zn2+ ion in MeCN/H2O (4 : 1 v/v), which can be attributed to the formation of both 1 : 1 and 1 : 2 metal-to-ligand complexes, as also confirmed by potentiometric measurements. Finally, crystals of [ZnL1(Ac)](Ac) (1), [CuL1(Cl)](Cl)·H2O (2) and [CuL3](NO3) (3) were grown and analysed by X-ray diffraction. 1 and 3 feature the metal center in a pseudo-octahedral coordination geometry coordinated also by the carbonyl group from one pendant arm, while in the case of 2, one of the six coordination sites in the final distorted octahedral geometry is occupied by the nitrogen donor from the urea group of one pendant arm.

Corrigendum: A Highly Active Bidentate Magnesium Catalyst for Amine‐Borane Dehydrocoupling: Kinetic and Mechanistic Studies

Abstract: A magnesium complex (1) featuring a bidentate aminopyridinato ligand is a remarkably selective catalyst for the dehydrocoupling of amine-boranes. This reaction proceeds to completion with low catalyst loadings (1 mol %) under mild conditions (60 °C), exceeding previously reported s-block systems in terms of selectivity, rate, and turnover number (TON). Mechanistic studies by in situ NMR analysis reveals the reaction to be first order in both catalyst and substrate. A reaction mechanism is proposed to account for these findings, with the high TON of the catalyst attributed to the bidentate nature of the ligand, which allows for reversible deprotonation of the substrate and regeneration of 1 as a stable resting state.

Two-Dimensional Networks of Thiocyanuric Acid and Imine Bases Assisted by Weak Hydrogen Bonds

Abstract: Co-crystals of thiocyanuric acid (TCA) and five multitopic bases are reported, and their structures are compared. The adducts of all five co-crystals form two-dimensional hydrogen-bonded sheets tha...

Reaction of imidazoline-2-selone derivatives with mesityltellurenyl iodide: a unique example of a 3c-4e Se→Te←Se three-body system embedding a tellurenyl cation

Abstract: The reactions of 1,1′-bis(3-methyl-4-imidazolin-2-selone)methane (L1) and 1,2-bis(3-methyl-4-imidazolin-2-selone)ethane (L2) with mesityltellurenyl iodide (MesTeI) [Mes = 2,4,6-Me3C6H2] yielded the neutral [L1·2MesTeI]·2CH2Cl2 and the ionic [L2·MesTe]2(MesTeI2)2 compounds, respectively, which were characterized by X-ray diffraction analysis. DFT (mPW1PW//LANL08d/def2-SVP) and NBO calculations, supported by structural and FT-Raman measurements, show that the latter compound represents the first example of an authentic mesityltellurenyl cation, [MesTe]+, stabilized within a [MesTe(B)2]+ (B = Lewis base) charge transfer adduct featuring a 3c-4e Se→Te←Se three-body system.