Tunable hydrophobicity: Efficient air filters for the protection against chemical warfare agents might be achieved by surface functionalization of the pores in robust metal–organic frameworks (MOFs) ...with fluoroalkyl residues and the precise control of their pore size (see picture). These MOFs capture harmful volatile organic compounds even under extremely moist conditions (80 % relative humidity).
Two new inherently chiral oligothiophenes characterized by the atropisomeric 3,3′‐bithianaphtene scaffold functionalized with fused ring bithiophene derivatives, namely ...4H‐cyclopenta2,1‐b3:4b′dithiophene (CPDT) and dithieno3,3‐b:2′,3′‐dpyrrole (DTP), were synthesized. The racemates were fully characterized and resolved into antipodes by enantioselective HPLC. The enantiomers were analyzed through different chiroptical techniques: electronic circular dichroism (ECD) and vibrational circular dichroism (VCD) were employed to attribute the absolute configuration (AC). Comparison of experimental and calculated VCD spectra confirmed the DFT calculated conformational characteristics. The compound functionalized with two CPDT units was oxidized with FeCl3, and ECD and CPL of the resulting material were measured. Circularly polarized luminescence (CPL) was measured to verify if inherently chiral oligothiophenes could be promising systems for chiral photonics applications.
C2‐symmetry, inherently chiral BT2‐based (BT2=bithianaphtene) electroactive molecules BT2‐CPDT2 and BT2‐DTP2 exhibit large CPL, associated with considerable decrease of central BT2‐unit dihedral angle from ground to excited state.
Temperature matters! The separation efficiency of complex mixtures of gases (acetylene, carbon dioxide, methane, nitrogen) and vapors (benzene, cyclohexane) by adsorption on ...ACu3(μ3‐OH)(μ3‐4‐carboxypyrazolato)3 (A@1) metal–organic frameworks depends on temperature and the extraframework cation A (see picture). NH4@1 also behaves as an oxidation catalyst.
Three recently synthesized neutral dinuclear carbonyl manganese complexes with the pyridazine bridging ligand, of general formula Mn2(μ-ER)2(CO)6(μ-pydz) (pydz = pyridazine; E = O or S; R = methyl or ...phenyl), have been investigated by cyclic voltammetry in dimethylformamide and acetonitrile both under an inert argon atmosphere and in the presence of carbon dioxide. This family of Mn(I) compounds behaves interestingly at negative potentials in the presence of CO2. Based on this behavior, which is herein discussed, a rather efficient catalytic mechanism for the CO2 reduction reaction toward the generation of CO has been hypothesized.
The dinuclear complex Re2(μ-Cl)2(CO)6(μ-4,5-(Me3Si)2pyridazine) gives in the solid state two polymorphs (yellow, 1Y, and orange, 1O), which can be either concomitantly or separately obtained on ...varying the crystallization rate. Both crystal phases exhibit intense photoluminescence from the lowest lying triplet metal-to-ligand charge transfer state, much stronger than in solution (quantum yields 0.56 and 0.52, for 1O and 1Y respectively, vs 0.06 in toluene), likely due to the restricted rotation of the Me3Si groups in the solid state. A clean, irreversible 1O → 1Y single-crystal-to-single-crystal phase transition occurs at 443 K, as revealed by variable temperature X-ray diffraction analysis. In spite of the absence of any strong intermolecular interactions in both forms, 1O and 1Y show very different absorption and emission maxima (λabs 370 and 393 nm, λem 534 and 570 nm, for 1Y and 1O, respectively). This behavior highlights the importance of the local organization of molecular dipoles in perturbing the photophysical properties of the molecule in the crystal.
Linear conjugated oligothiophenes of variable length and different substitution pattern are ubiquitous in technologically advanced optoelectronic devices, though limitations in application derive ...from insolubility, scarce processability and chain‐end effects. This study describes an easy access to chiral cyclic oligothiophenes constituted by 12 and 18 fully conjugated thiophene units. Chemical oxidation of an “inherently chiral” sexithiophene monomer, synthesized in two steps from commercially available materials, induces the formation of an elliptical dimer and a triangular trimer endowed with electrosensitive cavities of different tunable sizes. Combination of chirality with electroactivity makes these molecules unique in the current oligothiophenes literature. These macrocycles, which are stable and soluble in most organic solvents, show outstanding chiroptical properties, high circularly polarized luminescence effects and an exceptional enantiorecognition ability.
Too sexi by far: FeCl3 oxidation of the enantiopure antipodes of a chiral sexithiophene monomer characterized by a 3,3′‐bithianaphthene atropisomeric scaffold affords a mixture of shape‐persistent Dn symmetric oligothiophene macrocycles (see figure). Enantiopure dimers and trimers exhibit remarkable circularly polarized luminescence and exceptional enantiorecognition ability towards electrochemically active chiral probes.
Inherently Chiral Spider-Like Oligothiophenes Sannicolò, Francesco; Mussini, Patrizia R.; Benincori, Tiziana ...
Chemistry : a European journal,
July 25, 2016, Volume:
22, Issue:
31
Journal Article
Peer reviewed
Open access
The racemate of an inherently chiral “spider‐like” octathiophene monomer T83, in which chirality is generated by torsion in its backbone, was synthesized. The racemate was resolved into ...configurationally stable antipodes by HPLC on a chiral stationary phase. Electrooxidation of the enantiomers resulted in materials displaying high enantiorecognition ability towards the antipodes of some chiral probes. Moreover, the T83 racemate demonstrated great aptitude to stimulate formation of 3D rigid architectures if used as a cross‐linking monomer for molecular imprinting. This feature was exploited to devise a molecularly imprinted polymer‐based chemosensor selective for a thymine–adenine oligonucleotide.
Hyperbranched oligothiophenes display outstanding physicochemical properties. Hindered rotation around some specific interannular bonds provides these systems with additional relevant attributes: inherent chirality and high framework stiffness. The former endows the molecules with chiral discrimination properties, the latter with the unfading memory of templating species.
The highly porous and robust Ni(8)(OH)(4)(OH(2))(2)(4,4'-(buta-1,3-diyne-1,4-diyl)bispyrazolato)(6)(n) MOF can be used as a proof of concept for the incorporation and release of the non-conventional ...Ru(p-cymene)Cl(2)(pta) RAPTA-C metallodrug.
In this communication, a series of observations and data analyses coherently confirms the suitability of the novel metal–organic framework (MOF) ...Zn4(μ4-O)(μ4-4-carboxy-3,5-dimethyl-4-carboxy-pyrazolato)3 (1) in the capture of harmful volatile organic compounds (VOCs). It is worthy of attention that 1, whose crystal structure resembles that of MOF-5, exhibits remarkable thermal, mechanical, and chemical stability, as required if practical applications are sought. In addition, it selectively captures harmful VOCs (including models of Sarin and mustard gas, which are chemical warfare agents), even in competition with ambient moisture (i.e., under conditions mimicking operative ones). The results can be rationalized on the basis of Henry constant and adsorption heat values for the different essayed adsorbates as well as H2O/VOC partition coefficients as obtained from variable-temperature reverse gas chromatography experiments. To further strengthen the importance of 1, its performance in the capture of harmful VOCs has been compared with those of well-known materials, namely, a MOF with coordinatively unsaturated metal sites, Cu3(btc)2 and the molecular sieve active carbon Carboxen. The results of this comparison show that coordinatively unsaturated metal sites (preferential guest-binding sites) are ineffective for the capture of VOCs in the presence of ambient moisture. Consequently, we propose that the driving force of the VOC–MOF recognition process is mainly dictated by pore size and surface hydrophobicity.
Herein, the synthesis, crystal structure, and full characterization of a new soft porous coordination polymer (PCP) of (Cu2(dmcapz)2(OH2)DMF1.5)n (1) formulation, which is easily obtained in the ...reaction of CuX2 (X=Cl, NO3) salts with 3,5‐dimethyl‐4‐carboxypyrazole (H2dmcapz) is present. Compound 1 shows a copper(II) dinuclear secondary building unit (SBU), which is supported by two pyrazolate bridges and an unprecedented H2O bridge. The dinuclear SBUs are further bridged by the carboxylate ligands to build a diamondoid porous network. The structural transformations taking place in 1 framework upon guest removal/uptake has been studied in detail. Indeed, the removal of the bridging water molecules gives rise to a metastable evacuated phase (1 b) that transforms into an extremely stable porous material (1 c) after freezing at liquid‐nitrogen temperature. The soaking of 1 c into water allows the complete and instantaneous recover of the water‐exchanged material (1 a′). Remarkably, 1 b and 1 c materials possess structural bistability, which results in the switchable adsorptive functions. Therefore, the gas‐adsorption properties of both materials have been studied by means of single‐component gas adsorption isotherms as well as by variable‐temperature pulse‐gas chromatography. Both materials present permanent porosity and selective gas‐adsorption properties towards a variety of gases and vapors of environmental and industrial interest. Moreover, the flexible nature of the coordination network and the presence of highly active convergent open metal sites confer on these materials intriguing gas‐adsorption properties with guest‐triggered framework‐breathing phenomena being observed. The plasticity of CuII metal center and its ability to form stable complexes with different coordination numbers is at the origin of the structural transformations and the selective‐adsorption properties of the studied materials.
Water bridge: The plasticity of copper(II) ions and the presence of convergent active open‐metal sites in the porous network confers bistability and adsorption selectivity towards gases and vapors of industrial and environmental interest (see figure).
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