Electrochemical techniques for investigating redox active macromolecules

Phase Behavior and Electrochemical Properties of Highly Asymmetric Redox Coacervates

“…To discern which of these two mechanisms is dominant, we plotted Δ E p as a function of the square root of the scan rate (v 1/2 ) (Figure b). A linear relationship was obtained in all cases, which indicates that uncompensated resistance is small and that the system has a slow heterogeneous electron transfer at the electrode/solution interface. , In summary, the electrochemical response of the redox coacervate is controlled by both diffusional mass transport in solution and charge-transfer kinetics at the electrode/solution interface and, therefore, PEI/Fe­(CN) 6 3– coacervates are quasi -reversible electrochemical systems − (this conclusion is further supported by a detailed analysis of the effect of the scan rate on peak potential and current; see the discussion in the Supporting Information).…”

“…The peak separation Δ E p in both voltammograms is larger than the ideal value of 59.6 mV for a single-electron redox couple in solution and an electrochemical reversible process ( i.e. , a process where electron transfer at the electrode is much faster than the measurement timescale). − The fact that the peak separation, Δ E p , is larger than 59.6 mV indicates either a large ohmic drop (due to poor solution conductivity) or a quasi-reversible electrochemical response (due to sluggish heterogeneous electron transfer at the solution–electrode interface). To discern which of these two mechanisms is dominant, we plotted Δ E p as a function of the square root of the scan rate (v 1/2 ) (Figure b).…”

Vibrational Frequencies of Fractionally Charged Molecular Species: Benchmarking DFT Results against ab Initio Calculations

“…Significantly richer information on a given molecular species can be obtained if its (fractional) charge can be continuously tuned. Recent advances in nano/molecular electronics − and electrochemistry − made it possible to conduct such investigations experimentally. The average number of electrons of molecules adsorbed on biased electrodes can be continuously tuned by varying the bias. , Particularly promising in this direction are molecular junctions under electrochemical gating, ,, wherein an almost complete redox process can be achieved. , This is considerably more than electron transfers of up to ∼10% as inferred in earlier surface-enhanced Raman spectroscopy (SERS) experiments or using two terminal platforms .…”

Tuning the conformation of floppy molecules by charge transfer

“…Recent advances in nano-/molecular electronics [1][2][3][4][5][6] and electrochemistry 7,8 made it possible to overcome this limitation. When an electron travels across a molecule linked to two electrodes under applied bias V to form a single-molecule junction, a fractional (non-integral) V-dependent charge q (0 < |q| < 1) can arise.…”

“…Recent model studies 14 drew attention on the fact that the efficiency of the redox process can be substantially improved for EC-STM molecular junctions (EC: electrochemical, STM: scanning tunneling microscope). 1,2,[5][6][7][8]15,16 A much broader interval of charge values, ranging from a neutral molecular species (q ¼ 0) to an almost complete reduced molecular species (|q| ( 1), can be sampled under this experimental platform. To demonstrate theoretically this possibility, 14 available experimental data 2 for EC-STM single-molecule junctions based on viologen were employed.…”