Enhancement of electron-donating character in alkylated monopyrrolo-tetrathiafulvalene derivatives

Abstract

Herein we report the first synthesis of a monopyrrolotetrathiafulvalene (MPTTF) with two alkyl substituents, performed using a triphenylphosphine-mediated coupling reaction. An Ullmanntype N-arylation reaction was used to prepare a calixarene-based bis-MPTTF receptor, as well as an arylated mono-MPTTF derivative.Complexation studies with electron-deficient compounds showed strongly enhanced affinity of the alkyl-substituted MPTTF derivatives in comparison with the non-substituted MPTTF analogues.

Lower‐Rim‐Modified Calix[4]arene‐Pyrrolotetrathiafulvalene Molecular Tweezers

“…Such broadening effect is commonly explained by the formation of mixed-valence tetrathiafulvalene dimers (TTF 2 ) + * in the partially oxidized state, which is stabilized by intramolecular charge-transfer interactions between the proximal TTF and TTF + * moieties, [22] and it was commonly observed by us in our bis-TTF molecular systems. [13,14,17] Such behavior of derivatives 2 and 3, which is different from what we observed on all other our bis-TTF systems, implies that TTF moieties in 2 and 3 cannot easily come into spatial proximity with each other.…”

“…Addition of planar electron-deficient guests, such as tetracyanoquinodimethane (TCNQ) or 2,5,7-trinitro-9-dicyanomethylenefluorene (TNF), to a receptor solution leads to formation of deeplycolored charge-transfer complexes, easily visible to the naked eye. The binding constants reached as high as 2 × 10 5 m À 1 in CH 2 Cl 2 for Me-substituted TTF derivative [17] 1 c.…”

Molecular Hinges by Fusion of Pyrrole and Dithiin: Synthesis, Structure, Redox Chemistry and Host–Guest Complexation of Dipyrrolo‐1,4‐dithiins

“…Further non‐linear curve fitting the NMR titration data in nitromethane afforded a binding constant ( K a ) of 1.0 x 10 4 M −1 for the 1 : 1 complex of 1 a • CBPQT 4+ (Figure S7‐S9 and Table 2). A smaller K a of 4.4 x 10 3 M −1 was observed in acetonitrile, which was comparable to that of other sulfur‐containing compounds such as oligothiophenes [35] and tetrathiafulvalene derivatives [25,36] . As anticipated, 1 d exhibited a similar binding behavior (Figure S12–S14) but with a significantly smaller affinity by decreasing K a to nearly one‐tenth that of 1 a .…”

“…Conceivably, we envisaged that fusing the electron‐rich pyrrole with 1,4‐dithiins could afford exotic dipyrrolo‐1,4‐dithiins ( PD s) featuring ( i ) retained chemistry of a pyrrole; ( ii ) enhanced redox‐activity comparing with thianthrene; and ( iii ) adaptive hinge motion which might be mechanically regulatable via supramolecular interactions (Figure 1). Moreover, the binding affinity of a host–guest system could also be largely enhanced by exploiting the combined electron‐rich and dynamic nature of pyrrolo‐1,4‐dithiins as evidenced by the monopyrrolo‐tetrathiafulvalene [25] and 1,4‐dithiinosubporphyrins [26] . Nevertheless, to the best of our knowledge, only a 2,5‐diphenylpyrrole‐fused analogue has been so far reported as a by‐product with unclear mechanisms [27] .…”

Deciphering Noncovalent Interactions Accompanying 7,7,8,8‐Tetracyanoquinodimethane Encapsulation within Biphene[n]arenes: Nucleus‐Independent Chemical Shifts Approach

“…The complexation of TCNQ with modified calixarene hosts incorporating TTF functionalities has also been analyzed recently. [46,47] Electron transfer from the donor facilitates the reduction of TCNQ to form radical anions in solution and induce aromatic character in the central ring of its conjugated framework, rendering conformational flexibility. The radical is expected to exhibit qualitatively different structural and binding features.…”