Covalent integration of polymers and porous organic frameworks.

Covalent integration of polymers and porous organic frameworks (POFs), including metal-organic frameworks (MOFs), covalent organic frameworks (COFs) and hydrogen-bonded organic frameworks (HOFs), represent a promising strategy for overcoming the existing limitations of traditional porous materials. This integration allows for the combination of the advantages of polymers, i.e.

Functionalized Graphene via a One-Pot Reaction Enabling Exact Pore Sizes, Modifiable Pore Functionalization, and Precision Doping.

Functionalizing graphene with exact pore size, specific functional groups, and precision doping poses many significant challenges. Current methods lack precision and produce random pore sizes, sites of attachment, and amounts of dopant, leading to compromised structural integrity and affecting graphene's applications. In this work, we report a strategy for the synthesis of functionalized graphitic materials with modifiable nanometer-sized pores via a Pictet-Spengler polymerization reaction.

Engineering Screw Dislocations in Covalent Organic Frameworks.

We report the application of a Pictet-Spengler reaction to the synthesis of covalent organic frameworks (COFs) using functionalized terephthalaldehydes. The COFs produced show an increased propensity to generate screw dislocations and produce multilayered flakes when compared with other 2D-COFs. Using HRTEM, definitive evidence for screw dislocations was obtained and is presented.

Computationally directed manipulation of cross-linked covalent organic frameworks for membrane applications.

Two-dimensional covalent organic frameworks (2D-COFs) exhibit characteristics ideal for membrane applications, such as high stability, tunability and porosity along with well-ordered nanopores. However, one of the many challenges with fabricating these materials into membranes is that membrane wetting can result in layer swelling. This allows molecules that would be excluded based on pore size to flow around the layers of the COF, resulting in reduced separation.

Molecular Interactions and Layer Stacking Dictate Covalent Organic Framework Effective Pore Size.

Interactions among ions, molecules, and confining solid surfaces are universally challenging and intriguing topics. Lacking a molecular-level understanding of such interactions in complex organic solvents perpetuates the intractable challenge of simultaneously achieving high permeance and selectivity in selectively permeable barriers. Two-dimensional covalent organic frameworks (COFs) have demonstrated ultrahigh permeance, high selectivity, and stability in organic solvents.

Synthesis, Postsynthetic Modifications, and Applications of the First Quinoxaline-Based Covalent Organic Framework.

We report a new synthetic protocol for preparing highly ordered two-dimensional nanoporous covalent organic frameworks (2D-COFs) based on a quinoxaline backbone. The quinoxaline framework represents a new type of COF that enables postsynthetic modification by placing two different chemical functionalities within the nanopores including layer-to-layer cross-linking. We also demonstrate that membranes fabricated using this new 2D-COF perform highly selective separations resulting in dramatic performance enhancement post cross-linking.

The Influence of Disorder in the Synthesis, Characterization and Applications of a Modifiable Two-Dimensional Covalent Organic Framework.

Two-dimensional covalent organic frameworks (2D-COFs) have been of increasing interest in the past decade due to their porous structures that ideally can be highly ordered. One of the most common routes to these polymers relies on Schiff-base chemistry, i.e.

Hydrogen gas formation from the photolysis of rhenium hydrides - mechanistic and computational studies.

The photolysis of 4,4'-disubstituted, 2,2'-bipyridine fac-Re(bpy)(CO)H derivatives produces stoichiometric H gas. The rate of production varies greatly depending on the electronic nature of the disubstituted bipyridine (bpy) with halogenated substituents increasing the rate. Isotope labeling studies along with B3LYP geometry optimization DFT modeling studies indicate a mechanism involving a Re-H-Re bridging complex that leads to a dimeric Re-Re(η-H) state prior to dissociating H gas.

A Highly Ordered Nanoporous, Two-Dimensional Covalent Organic Framework with Modifiable Pores, and Its Application in Water Purification and Ion Sieving.

The preparation of membranes with high selectivity based on specific chemical properties such as size and charge would impact the efficiency of the world's energy supply, the production of clean water, and many other separation technologies. We report a flexible synthetic protocol for preparing highly ordered two-dimensional nanoporous polymeric materials (termed covalent organic frameworks or COFs) that allow for placing virtually any function group within the nanopores. We demonstrate that membranes, fabricated with this new family of materials with carboxylated pore walls, are very water permeable, as well as highly charged and size selective.

An N-heterocyclic carbene phenanthroline ligand: synthesis, multi-metal coordination and spectroscopic studies.

Dimetal complexes of a new N-heterocyclic carbene/phenanthroline ligand have been synthesized. Coordination of both ruthenium and rhenium to the phenanthroline moiety in combination with platinum at the carbene moiety are reported. Steady-state and time-resolved optical absorption and photoluminescence spectra were obtained for the complexes.

Facile synthesis and platinum complexes of 4',5,5''-trisubstituted-2,2':6',2''-terpyridines.

The synthesis of trisubstituted 4',5,5'' terpyridines is described. The strategy begins with synthesis of 2-acetyl-5-bromopyridine (3) from 2,5-dibromopyridine, substitution of the bromine in 3 using a variety of metal-catalyzed reactions and then formation of the terpyridine using the Krohnke reaction. The complexes have been prepared by reaction of [Pt(PhCN)(2)Cl(2)] with the appropriate silver salt followed by addition of the terpyridyl ligand.

Heptanosides from galactose-derived oxepenes via stereoselective addition reactions.

Addition reactions to a 3,4-anhydroheptanose gave heptanoside analogues of carbohydrate derivatives in good to excellent stereochemical purity. Characterization of the products by (1)H and (13)C NMR, COSY, HSQC-DEPT, HMBC, 1D TOCSY, and NOE experiments were performed to obtain the stereochemistry of addition. The 3,4-anhydroheptanose used in this study is obtained from the ring-expansion of a cyclopropanated galactal and thus demonstrates the synthetic utility of heptanose synthesis via cyclopropanated carbohydrates.

Improved synthesis of dicyclohexylidene protected quebrachitol and its use in the synthesis of L-chiro-inositol derivatives.

A modified synthesis of 1L-1,2:3,4-di-O-cyclohexylidene-5-O-methyl-chiro-inositol has been accomplished that improves the overall procedure, yield, and environmental aspects of its formation. Several inositol analogues have been prepared from this intermediate for testing as biosynthetic inhibitors of glycosyl-phosphatidylinositol (GPI) anchor formation.

Inositols as chiral templates: 1,4-conjugate addition to tethered cinnamic esters.

The 1,4-addition of thio nucleophiles to chiro-inositols containing a cinnamyl Michael acceptor proceeded with excellent diastereochemical induction and good yields. Cleavage of the inositol auxiliary provides beta-thio hydrocinnamic acids in >99% ee's.

Monoesterification of di-O-isopropylidene and di-O-cyclohexylidene chiro-inositols.

Monoesterification of D- or L-chiro-inositols protected as diacetals proceeds in excellent selectivity and yields. The metal-catalyzed, one-step reaction proceeds at room temperature under an air atmosphere and has been developed using a range of examples.

Potassium channel activators based on the benzopyran substructure: synthesis and activity of the C-8 substituent.

The synthesis of a series of methoxy bearing 2,2-dimethyl-2H-1-benzopyrans have been achieved for testing as potassium channel activators. The synthesis involves formation of 6-cyano-8-methoxy-2,2-dimethyl-2H-1-benzopyran from vanillin, epoxidation, then ring opening of the epoxide with nitrogen nucleophiles to produce the new benzopyrans. Biological testing showed a dramatic decrease in activity thus revealing an important site of activity in this class of compounds.