The manner of bonding between constituent atoms or molecules invariably influences the properties of materials. Perhaps no material family is more emblematic of this than porous frameworks, wherein the namesake modes of connectivity give rise to discrete subclasses with unique collections of properties. However, established framework classes often display offsetting advantages and disadvantages for a given application. Thus, there exists no universally applicable material, and the discovery of alternative modes of framework connectivity is highly desirable. Here we show that chalcogen bonding, a subclass of σ-hole bonding, is a viable mode of connectivity in low-density porous frameworks. Crystallization studies with the triptycene tris(1,2,5-selenadiazole) molecular tecton reveal how chalcogen bonding can template high-energy lattice structures and how solvent conditions can be rationalized to obtain molecularly programmed porous chalcogen-bonded organic frameworks (ChOFs). These results provide the first evidence that σ-hole bonding can be used to advance the diversity of porous framework materials.
The present work describes the design and synthesis of a series of rhodium and iridium dimers [(η 5ring)MCl] 2 (μ 2 -Cl) 2 (where (η 5 -ring)MCl = (η 5 -Me 4 C 5 R)Rh-(III)Cl or (η 5 -Me 4 C 5 R)Ir(III)Cl) using a new and efficient 1 h procedure. Rhodium and iridium dimeric complexes were synthesized via a microwave reaction. The modified HMe 4 C 5 R (R = isopropyl, n-butyl, isobutyl, sec-butyl, n-pentyl, n-hexyl, nheptyl, n-octyl, phenyl, benzyl, phenethyl, cyclohexyl, and cyclopentyl) type ligands were synthesized by reaction of 2,3,4,5-tetramethylcyclopent-2-en-1-one with the respective Grignard reagent (RMgX), followed by elimination of water under acidic conditions to produce the tetramethyl(alkyl or aryl)cyclopentadienes in moderate to excellent yields (40−98%). Reaction of the HMe 4 C 5 R ligands with [M(COD)](μ 2 -Cl) 2 (M = Rh, Ir; COD = 1,5-cyclooctadiene) gave the dimeric complexes [(η 5 -Me 4 C 5 R)MCl] 2 (μ 2 -Cl) 2 in yields ranging from 47% to 96%. The derivatized dimers were tested for antimicrobial activity, showing activity against Mycobacterium smegmatis and improved activity with derivatized R groups against Staphylococcus aureus and MRSA 43300. The characterization of these complexes was completed by NMR spectroscopy, single-crystal X-ray diffraction, high-resolution mass spectrometry, and elemental analysis.
A series of Rh III and Ir III half-sandwich compounds of the type [(η 5 -Cp* R )M(β-diketonato)Cl] were synthesized and characterized, including 17 X-ray crystallographic structures. In general, the complexes were synthesized in short reaction times and in good yield. The antimicrobial properties of these complexes were tested against a variety of microbes, and several complexes were found to have good activity against Mycobacterium smegmatis.
Fluorinated molecules containing reactive functionalities are of great interest to the materials community as these compounds can be used to prepare fluorinated polymers with desirable physical and electronic properties. Despite their potential, many of these compounds are limited by their synthesis which generally requires transition-metal-catalyzed coupling reactions or harsh fluorinating conditions. Perfluoroheteroaromatic compounds provide a unique solution to this problem as compounds such as perfluoropyridine can undergo SNAr reactions with a wide range of simple nucleophiles in a controlled and regioselective manner. Herein we report the transition-metal-free synthesis of a pool of highly soluble high aromatic content (HAC) perfluoropyridine-based thermosetting precursors and compounds of interest which can be easily obtained from readily available chemical precursors using simple nucleophilic chemistries. These thermally active monomers cure readily, in 350–400 °C temperature ranges, into highly densified polyaryelene networks and demonstrate decomposition temperatures well above 400 °C and high char yields at 900 °C, making these promising materials for high-temperature applications as well as templates for carbon-based nanomaterials.
Polymer functionality greatly determines many of the key properties of these materials, such as glass-transition temperature, electrical and thermal conductivity, thermal stability, mechanical strength, and processability. Despite the importance of polymer functionality in determining material properties, the synthesis of functional polymers, with well-defined molecular weights and compositions, can still present a significant challenge, with many of the methods related to pre- or postpolymerization modification lacking synthetic scope, or requiring harsh functionalization conditions or transition-metal coupling reactions to install the desired functionality. Perfluoroaromatic systems are promising for the preparation of novel polymer architectures given that they can be readily functionalized using simple nucleophilic chemistries under very mild basic conditions. While promising, these systems have displayed some drawbacks. Previous work has shown that perfluoroaromatics, such as perfluoropyridine, can demonstrate a high degree of chemical reversibility with heteroatom nucleophiles. If the synthetic potential of these systems is to be realized, then a strategy for the rational design of stable monomers must be developed. Herein, we report the design, synthesis, and characterization of a series of unexplored heteroatom-based ring-opening metathesis polymerization (ROMP)-active monomers containing a reactive perfluoropyridine pendent group, which can be used to readily prepare a wide variety of aryl ether-functionalized polymers, using both pre- and postpolymerization modification strategies. We also establish a direct connection between the dihedral angle of the monomer and its propensity to undergo reversible addition reactions, establishing functional criteria for the design of pre- and postmodifiable systems.
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