1′,1′′′-Bis(ethynyl)biferrocene as a Linking Group for Gold, Ruthenium, and Osmium Fragments: Synthesis, Solid State Structures, and Electrochemical, UV−Vis, and EPR Spectroscopical Studies

Abstract

A series of organometallic mono-and disubstituted bis(alkynyl)biferrocenes of type (L n MCtC)-(HCtC)bfc (L n M ) (η 5 -C 5 H 5 )(Ph 3 P) 2 Ru (8a), (η 5 -C 5 H 5 )(Ph 3 P) 2 Os (8b), (η 5 -C 5 H 5 )(dppf)Ru (8c); bfc ) 1′,1′′′-biferrocenyl, ((η 5 -C 5 H 4 ) 2 Fe) 2 ; dppf ) 1,1′-bis(diphenyl)phosphanyl ferrocene, (η 5 -C 5 H 4 PPh 2 ) 2 Fe) and (L n MCtC) 2 bfc (L n M ) (Ph 3 P)Au ( 6), (η 5 -C 5 H 5 )(Ph 3 P) 2 Ru (9a), (η 5 -C 5 H 5 )(Ph 3 P) 2 Os (9b), (η 5 -C 5 H 5 )(dppf)Ru (9c)) have been synthesized from (HCtC) 2 bfc (4) with either (Ph 3 P)AuCl (5) in the presence of HNEt 2 /[CuI] (synthesis of 6) or L n MX (L n MX ) (η 5 -C 5 H 5 )(Ph 3 P) 2 RuCl (7a); (η 5 -C 5 H 5 )(Ph 3 P) 2 OsBr (7b); (η 5 -C 5 H 5 )(dppf)RuCl ( 7c)) together with [H 4 N]PF 6 and KOtBu (synthesis of 8 and 9), respectively. The structures of 6, 8b, 9a, 9b, and 9c in the solid state were determined by singlecrystal X-ray structure analysis, showing unsymmetrical (8) or symmetrical geometries (6, 9), with almost eclipsed conformations or approximately midway positions between the fully eclipsed and the fully staggered conformation of the bfc cyclopentadienyl rings and with anti geometry of the linear ethynyl connecting units. UV-vis and NIR spectroscopic measurements suggest a weak interaction between the appropriate metal atoms. The associated radical cations were in situ generated by stepwise chemical oxidation and characterized by continuous wave electron paramagnetic resonance (EPR) investigations in X-band performed at low temperature.

Ferrocenyl‐Pyrenes, Ferrocenyl‐9,10‐Phenanthrenediones, and Ferrocenyl‐9,10‐Dimethoxyphenanthrenes: Charge‐Transfer Studies and SWCNT Functionalization

“…For neutral 5 b and 12 , as expected, no absorptions between 800 and 3000 nm were detected, whereas mono‐oxidation of 5 b and 12 ( E ≈500 mV vs. Ag/Ag + ) gave mixed‐valent species [ 5 b ] + and [ 12 ] + and hence a broad absorption within this area (800–3000 nm) was observed. A further increase in the potential resulted in a decrease of this band, which is characteristic for intervalence charge transfer excitations (Figure , Figures SI24 and SI25 in the Supporting Information) . Please note that the low Δ E °′ values ( 5 b : 100 mV, 12 : 80 mV) and therefore the small comproportionation constants ( 5 b : K c =70.0, 12 : K c =29.9) lead, in the best case, to a mixture consisting of an equilibrium of 73 % mixed‐valent monocationic [ 12 ] + as well as 13.5 % neutral 12 and di‐cationic species [ 12 ] 2+ each.…”

“…Af urtheri ncrease in the potentialr esulted in ad ecrease of this band, which is characteristic for intervalencec harget ransfer excitations (Figure 9, Figures SI24 and SI25 in the Supporting Information). [85][86][87][88][89] Please note that the low DE8' values (5b:1 00 mV, 12:8 0mV) and therefore the small comproportionation constants( 5b: K c = 70.0, 12: K c = 29.9) lead, in the best case, to am ixture consistingo fa ne quilibrium of 73 %m ixed-valent monocationic [12] + as well as 13.5 %n eutral 12 and di-cationic species [12] 2 + each. As the composition of this equilibrium is not determinable by using an OTTLE cell, the extinctionv alues are associated with considerable uncertainties.…”

Novel paste electrodes based on phosphonium salt room temperature ionic liquids for studying the redox properties of insoluble compounds

“…In recent years, the development of compounds with redox-active metal centers has attracted considerable attention, since they can be applied as new materials with novel chemical, physical, and/or electronic properties in the field of material science [63][64][65][66][67][68]. Therefore, homo-and heterodinuclear complexes connected by carbon-rich π-conjugated organic units were designed as simple models for molecular wires [64,[69][70][71][72][73][74] and novel electro-active materials [75,76].…”

Functionalised Biferrocene Systems towards Molecular Electronics

“…Other reports have utilised the biferrocene motif within wire‐like structures, and shown their suitability as SAMs (self‐assembly monolayers) as well as bridging units between other metal centres . These studies indicate that the biferrocene motif can be a better conductor than a single ferrocene unit, for example allowing electron transfer between terminating metals through 1,1′‐bis(ethynyl)biferrocene systems . The versatility of uses, the excellent electronic characteristics and the variation in synthetic strategies that can be achieved, make the biferrocene motif an attractive unit within the field of molecular electronics …”