Concerning the Electronic Control of Torsion Angles in Biphenyls

Abstract

In the search for evidence to establish the effect of π conjugation on the variation of the equilibrium torsion angle (θ eq ) in push-pull 4,4Ј-disubstituted biphenyls, a systematic Hammett DFT study has been carried out. The study shows that although reasonable and intuitive, the through-conjugation between donor and acceptor substituents in these systems is only of some relevance when strong donor and strong charged acceptors are involved. In these cases, changes in

Conformational Tuning of the Intramolecular Electronic Coupling in Molecular‐Wire Biruthenium Complexes Bridged by Biphenyl Derivatives

“…[34][35][36] Studies on the effect of variouso rganic bridge ligands on the redox processes of bimetallicc omplexes will not only help to mimic the intramolecular charge displacement, but are also crucially required for developingm olecular electronic devices. Biphenyl linkers, which consist of two aromatic rings connected by aC À Cs ingle bond, have recently attracted considerable interest as bridges spanning terminally appended redoxactive moieties [43][44][45] or anchoring groups. [46][47][48][49][50][51][52][53] This is done with the hope that modulating or even controlling the degree of torsion of the two phenylr ings might allow one to exert control over ET between the terminal redoxsites or in as inglemolecular junction.…”

“…Biphenyl linkers, which consist of two aromatic rings connected by a CC single bond, have recently attracted considerable interest as bridges spanning terminally appended redox‐active moieties43–45 or anchoring groups 46–53. This is done with the hope that modulating or even controlling the degree of torsion of the two phenyl rings might allow one to exert control over ET between the terminal redox sites or in a single‐molecular junction.…”

Control of Molecular Conformation and Crystal Packing of Biphenyl Derivatives

“…[28] This effect can also be obtained by controlling the electronic properties of the BP moiety by the substitution of hydrogen atoms at selected positions with electron donating and electron withdrawing substituents. [29][30][31][32][33] In a study of asymmetrically functionalized BP, it has also been proposed that conformational control can be achieved by the action of a local electric field. [34] Usually, the electronic control in BP and substituted biphenyls is rationalized as a control of the electron delocalization between the phenyl rings which is assumed to be larger at small torsion angles.…”

Examining conductance values in the biphenyl molecular switch with reduced density matrices

“…One of the long‐standing goals of molecular electronics is to build nanoscale, controllable single‐molecule electronic switches. A wide range of potential molecular switches with a variety of different control mechanisms including but not limited to light‐controlled, chemically controlled, and spin‐controlled switches have been proposed [1–20]. While notable progress has been made in the synthesis and characterization of single‐molecule switches, many challenges remain for both experimentalists and theorists before practical nanoscale molecular switches can be realized.…”