The encapsulation of a fluoride ion in a trigonal prismatic CuII6-pyrazolato cage results in a small expansion of the Cu6-host. The structural, electronic and magnetic features of the Cu6-complex, containing an endohedral fluoride in the rare μ6-F coordination mode, are compared with those of the parent complex with a vacant Cu6-cage.

•Two isostructural silver-triazolato cationic MOFs, containing hexagonal channels, are studied.•The MOF lattices expand upon CO2 sorption at 10 atm of pressure.•Reversible sorption/desorption profiles at 1 atm, become hysteretic at 10 atm.•CO2 is selectively sorbed, forming weak van der Waals interactions with the sorbents.•The CO2 sorption sites, proximal to organic moieties, have been identified by DFT calculations.A new silver-triazolate metal–organic framework (MOF), {Ag3[Ag5(μ3-3,5-tBu2tz)6](BF4)2}n (2), has been prepared and structurally characterized. The CO2 sorption properties of this new MOF and previously reported isostructural analog {Ag3[Ag5(μ3-3,5-Ph2tz)6](NO3)2}n (1), were determined experimentally and probed theoretically by a density functional (DF) method. The structures of 1 and 2 are based on flexible Ag5tz6-structural building units (SBUs), which allow the expansion/contraction of the structure, depending on either the steric requirements of the pendant groups – tBu, or Ph – of the SBUs, or the pressure of the gaseous sorbate. Both silver-triazolate MOFs sorb CO2 preferentially to N2, O2, CH4 and H2. DF calculations show CO2 to be bound by van der Waals forces to the organic moieties of the porous framework. This work shows that van der Waals interactions of CO2 and the aromatic and aliphatic hydrocarbons of silver-triazolate MOFs are sufficient to achieve preferential sorption of CO2.A flexible nanoporous silver-triazolato MOF expands as it adsorbs CO2 selectively, forming weak van der Waals interactions between CO2 and aromatic (or alkyl) groups lining the hexagonal channels of sorbent.

The encapsulation of a fluoride ion in a trigonal prismatic CuII6-pyrazolato cage results in a small expansion of the Cu6-host. The structural, electronic and magnetic features of the Cu6-complex, containing an endohedral fluoride in the rare μ6-F coordination mode, are compared with those of the parent complex with a vacant Cu6-cage.

A combination of SQUID and pulsed high-field magnetometry is used to probe the nature of mixed valency in an FeIIFe7III cluster. DFT-computed spin Hamiltonian parameters suggest that antiferromagnetic coupling dominates, and that electron transfer both between the four irons of the cubane core (t1) and between a cubane and three neighboring irons (t2) is significant. Simulations using the computed parameters are able to reproduce the key features of the measured effective magnetic moment, μeff(T), over the 2 < T < 300 K temperature range. In contrast, the field dependence of the molar magnetization, Mmol, measured at 0.4 K is inconsistent with substantial electron transfer: only values of t2 ∼ 0 place the separation between ground and first excited states in the region indicated by experiment. The apparent quenching of the cubane–outer electron transfer at very low temperatures indicates that vibronic coupling generates one or more shallow minima on the adiabatic potential energy surfaces that serve to trap the itinerant electron in the cubane core.