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The solid‐state chemistry of a series of seven ortho‐bis(alkylamido)ethylenedithiotetrathiafulvalene derivatives EDT‐TTF‐(CONHR)2(R=Me, 1; Et, 2; Pr, 3; Bu, 4; Pent, 5; Hex, 6; and Bz, 7), in their neutral and one‐electron‐oxidized, radical cation states, was investigated with an eye on the topology of intra‐ and intermolecular hydrogen‐bond motifs. In the case of neutral, monomolecular solids, an intramolecular NH⋅⋅⋅O hydrogen bond seals a constrained seven‐membered ring for 1, 2, 3, and 7, which is disrupted in butyl derivative 4in favor of an antiparallel ladder at the expense of any intramolecular hydrogen bond. In the solid‐state, the competition between intra‐ and intermolecular hydrogen bonding observed in solution depends on the packing of the molecules. Electrocrystallization of methyl derivative 1with ReO4−or ClO4−, two anions of different volumes but otherwise identical charge and symmetry, revealed a fine sensitivity of the constrained seven‐membered ring to the internal chemical pressure exerted by the anion. [1]2.+ReO4(σRT=8.5 S cm−1, activation energy Δ=600 K at high temperature) and β′′‐[1]2.+ClO4(σRT=0.03 S cm−1, Δ=1600 K; under pressure at room temperature, the conductivity increases by three orders of magnitude up to 17 kbar with a linear variation of the activation energy with pressure, Δ=aPwith a=0.202 106K kbar−1) have vastly different architectures, dimensionalities, electronic structures, and collective properties, a consequence of the presence of the closed or open structural isomers in one or the other. This exemplifies the flexibility of functionalized TTF derivatives, even when the functional group is directly attached to the electro‐active core. This allows an analogy to be drawn with tetrafunctionalized metallocenes, in which such flexibility has already been observed. The experimental data are supported by theoretical calculations of the energy profile of a model molecule on rotation of the amido groups.

An in‐depth analysis of a set of 21 layered structures of metallic pseudopolymorphs of general formulation, β″‐(BEDT‐TTF)4⋅(guest)n⋅[Re6Q6Cl8], (BEDT‐TTF=bis‐ethylenedithiotetrathiafulvalene; Q = S, Se; guest = H2O, 1,4‐dioxane, THF, CCl4, C2H5OH, CHCl3, CH2ClI, CH2ClBr, CH2Cl2, CH2OH‐CH2OH, C5H5N, CH3COCH3, 2‐hydroxy‐tetrahydrofuran, CH3CN, CS2, C6H6), with diverse low‐temperature behaviors, which differ solely by the nature of the cosolvent molecule selectively included during the electrocrystallization process, reveals a precise set of weak HO‐H⋅⋅⋅Cl‐μ‐Re, (C‐H)BEDT‐TTF⋅⋅⋅Cl‐μ‐Re, C‐H⋅⋅⋅Oguest, (C‐H)guest⋅⋅⋅Cl‐μ‐Re hydrogen bonds at the organic–inorganic interface, none of which dominates any of the others and whose balance is adjusted upon substitution of one guest molecule by another. The electronic structure of the host adjusts to the weak perturbation imposed by exchanging the guest molecules and by balancing the former interfacial interactions; this correlates to a net activation of up to 0.1 eV of the energy of the HOMO level of one of the two donors, while keeping the pattern of HOMO–HOMO intermolecular interactions in the donor layer essentially unaltered. It is suggested that this controls the stability of the metallic state at low temperature or the occurrence of a metal‐to‐insulator phase transition for particular guests along the series. It is concluded that by allowing for numerous tiny modifications at the organic–inorganic interface within a single, robust host structure, one sees a concerted, inherently weak structural response of the system that is proportional to the magnitude of the underlying, equally weak activation of the HOMO energy of a fraction of the π‐donor molecules within the slabs; this has a sizeable influence on the macroscopic transport properties of the system.