The influence of intermolecular coupling on electron and ion transport in differently substituted phthalocyanine thin films as electrochromic materials: a chemistry application of the Goldilocks principle

Abstract

Optimum molecular substitution in organic thin films is established to facilitate electron and ion transport and, thereby, fast reversible electrochromic switching.

Synthesis, X-ray Structures, and Optical and Magnetic Properties of Cu(II) Octafluoro-octakisperfluoro(isopropyl)phthalocyanine: The Effects of Electron Addition and Fluorine Accretion

“…The substitution of aromatic hydrogen in H 16 Pc with fluorine indeed enhances the electronic-accepting capability of the Pc, as well as its thermal and chemical robustness, beneficial properties for catalytic applications. The formal replacement of the eight peripheral F atoms of F 16 PcCu with iso -C 3 F 7 -groups, to give F 64 PcCu, shifts the redox potentials of Cu II F x Pc toward even more positive values. ,,, A positive shift of about 0.4 V is observed for the F 64 Pc scaffold vs F 16 Pc. Notably, the positive shift is metal-independent since the frontier orbitals consist of an atomic orbital of the ligand.…”

“…The ligand-only g = 2.0000 value is consistent with g = 2.003–2.009 measured for the solution, ligand-only signal of [Zn­(F 64 Pc •3– )] − . , Compared with F 64 Pc •3– , the intramolecular couplings between Cu II and F x Pc •3– , x = 8 and 16, namely, −10.8 and −5.6 cm –1 , respectively (Table ) are at least 1 order of magnitude larger. , As the degree of fluorination increases, the intramolecular magnetic coupling decreases, a trend consistent with the notion of enhanced spin density transfer to acceptor fluoro-substituents as x increases. Thus, the weakest coupling in [Cu II (F 64 Pc) •3– ] − could be explained by the extreme electron deficiency of its Pc core. , The geometry around the copper­(II) atoms most probably does not affected the J values since, according to the SHAPE 2.1, estimation, for all three anions with x = 8, 16, and 64, the geometry of copper­(II) is very close to square-planar, D 4 h symmetry. As a control experiment, the possibility of inter-Pcs coupling, mediated by the π-stacked solvents, was considered.…”

“…The largest redox shift has been achieved to date by the introduction of eight, bulky perfluoro­(isopropyl) ( i -C 3 F 7 ) groups at the peripheral positions of perfluoro Pcs, forming 1,4,8,11,15,18,22,25-octafluoro-2,3,9,10,16,17,23,24-octakisperfluoro­(isopropyl)­phthalocyanine, present in MF 64 Pc, M = Cu II , Co II , Zn II , V IV O, etc. The complexes enhanced solubility in organic solvents, and chemical stability rendered them suitable for applications in photodynamic therapy, , catalysis, − and materials for electrochromic displays. − Their strong electron acceptor ability allows the reversible addition of 1 or 2 electrons to form [M­(F 64 Pc •3– )] − or [M­(F 64 Pc 4– )] 2– , while electron loss is suppressed. ,,, Reduction or oxidation of Pcs yield species with an unpaired electron delocalized over the macrocycles. This electron can participate in the magnetic coupling of spins or high conductivity. , Moreover, in the case of paramagnetic central metal atoms, an unpaired electron localized on metal can interact with the conducting electron delocalized over the macrocycles leading to giant magnetoresistance. , Generally, metal phthalocyanine anions are very air-sensitive due to strongly negative reduction potentials but that is not true for the air-stable radical trianions F 64 Pc •3– .…”

Metallo‐phthalocyanines Containing 1,3,4‐oxadiazole Substituents: Synthesis, Characterization, Electrochemical and Spectroelectrochemical Properties

“…It has been reported that MPcs having rich redox and coordination properties can be used as an electrocatalyst in different application areas such as battery, [30] photovoltaic cells, [31] water splitting, [32] reduction of CO 2 , [33] supercapacitors [34] and electrochemical sensors [35] . In addition to their catalytic properties, their color changes during redox reactions depending on the substituted groups of the MPcs allow using in electrochromic applications [36–38] …”

“…[35] In addition to their catalytic properties, their color changes during redox reactions depending on the substituted groups of the MPcs allow using in electrochromic applications. [36][37][38] Electrochemical characterization of synthesized MPcs (6-9)was carried out by the CV and SWV techniques in DCM/TBAP electrolyte. The SWV technique was used for detailed peak analysis with high sensitivity.…”