J.A.J.M. Vekemans

Developments in the chemistry and band gap engineering of donor–acceptor substituted conjugated polymers

Abstract This paper reviews the tools to manipulate and minimize the band gap of conjugated (co)polymers. The effects of minimization of the bond length alternation and of the incorporation of donor-π-acceptor units are discussed in particular. A systematic study of a series of alternating donor–acceptor oligomers has revealed the achievable limits and allowed for a prognosis of the performance of corresponding copolymers. The decisive influence of the LUMO eigenvectors of the acceptors on the band gap is highlighted. A new synthesis of benzo[1,2-c:4,5-c]bis[1,2,5]thiadiazole containing donor–acceptor monomers and their acid-catalyzed polymerization are described. Finally, band gap tuning by appropriate substitution, conformational adjustment and mesoscopic ordering is discussed.

Band‐Gap Engineering of Donor–Acceptor‐Substituted π‐Conjugated Polymers

Some practical guidelines for the design of novel low-band-gap systems. Various donor–acceptor π-conjugated oligomers with different chain lengths containing electron-donating thiophene or pyrrole rings and electron-withdrawing 2,1,3-benzothiadiazole (like the one shown here) or quinoxaline rings have been synthesized by Stille cross-coupling. The UV/Vis absorption behavior of these systems is used to give guidelines for donor–acceptor based low-band-gap or even intrinsically conducting polymers.

Lyotropic Liquid‐Crystalline Behavior in Disc‐Shaped Compounds Incorporating the 3,3′‐Di(acylamino)‐2,2′‐bipyridine Unit

An extended‐core liquid crystal (LC) based on the 3,3′‐di(acylamino)‐2,2′‐bipyridine unit is investigated with respect to its behavior in alkane solvents. It is demonstrated that the lyotropic mesomorphism observed in dodecane can be tuned by varying the concentration of the sample, and the columns can be switched in an electric field. The Figure shows the structure of the columnar nematic phase present in dodecane containing 15.7 wt.‐% LC.

Enantioselective reduction of C=O and C=N compounds with NADH model N,N,1,2,4-pentamethyl-1,4-dihydronicotinamide

Abstract The scope and mechanism of enantioselective hydride transfer from NADH model 4 to prochiral CO and CN compounds were investigated. Efficient chirality transfer from 4 to α-keto esters and α-methoxycarbonylimino esters was achieved. The resemblance in reactivity and stereochemistry of the prochiral CO and CN-CO2Me functionalities in the hydride transfer reaction is attributed to the intervention of a similar Mg(ClO4)2-mediated ternary complex.

Alternating copolymer of pyrrole and 2,1,3-benzothiadiazole

The alternating copolymer of pyrrole and 2,1,3-benzothiadiazole is synthesized together with a set of corresponding oligomers, yielding hydrogen bonded ladder structures with push-pull character and an absorption band up to λmax 700 nm.

Synthesis, Estrogen Receptor Binding, and Tissue Distribution of a New Iodovinylestradiol Derivative (17α,20E)-21-[123I]Iodo-11β-Nitrato-19-Norpregna-1,3,5(10),20-Tetraene-3,17-Diol (E-[123I]NIVE)

We have synthesized and evaluated E-11beta-nitrato-17alpha-iodovinylestradiol (E-NIVE; E-3c) and its 123I-labelled form, as a new potential radioligand for imaging of estrogen receptor (ER)-positive human breast tumors. E-[123I]NIVE was prepared by stereospecific iododestannylation of the E-tri-n-butylstannylvinyl precursor (E-2c), obtained from reaction of 11beta-nitrato-estrone (8) with E-tributylstannylvinyllithium. In competitive binding studies, E-NIVE proved to have high binding affinity for both the rat and the human ER (Ki 280-730 pM), without significant binding to human sex hormone binding globulin. Distribution studies in normal and mammary tumor-bearing rats showed specific ER-mediated uptake of E-[123I]NIVE in the estrogen target tissues, i.e., uterus, ovaries, pituitary, and hypothalamus, but not in the mammary tumors. Selective retention in these target tissues, including tumor tissue, resulted in significant increases over time for the target tissue-to-muscle uptake ratios, but not for the target tissue-to-fat uptake ratios. The tumor-to-fat uptake ratio even appeared constantly below 1. In the primary estrogen target tissues, E-[123I]NIVE displayed high specific ER-mediated uptake and retention, which resulted in moderate target-to-nontarget tissue uptake ratios. In contrast, in tumor tissue, E-[123I]NIVE uptake appeared to be rather low and not ER-specific. As a consequence, E-[123I]NIVE appears to be a less favorable radioligand for ER imaging in breast cancer than the previously studied stereoisomers of 11beta-methoxy-17alpha-[123I]iodovinylestradiol (E- and Z-[123I]MIVE; [123I]E- and [123I]Z-3b).

NADH model mediated reduction of C=N substrates: enantioselective synthesis of D- and L-phenylglycinates

Abstract Hydride transfer from N,N,1,2,4-pentamethyl-1,4-dihydronicotinamide, 1 , to methyl 2-methoxycarbonylimino-phenylacetate, 3 , was accomplished in an optical yield ⪰95%.

Hydrogen-bonded porous solid derived from trimesic amide

N,N′ ,N″-Tris(3-pyridyl)trimesic amide, 1, forms a unique P symmetrical crystal containing pores with a mean diameter of 8.26 A.