In the covalently linked 2D coordination network {[Fe(bbtr)₃](BF₄)₂}_∞, bbtr = 1,4-di(1,2,3-triazol-1-yl)butane, the iron(II) centers stay in the high-spin (HS) state down to 10 K. They can, however, be quantitatively converted to the low-spin (LS) state by irradiating into the near-IR spin allowed ⁵dd band and back again by irradiating into the visible ¹dd band. The compound shows true light-induced bistability below 100 K, thus, having the potential for persistent bidirectional optical switching at elevated temperatures.

Two molecules containing two phenylphosphaalkene moieties linked by an anthracene (1) or by a naphthalene (2) ring have been synthesized and their crystal structures have been determined. While electrochemical measurements show that these two systems are easily reduced, EPR spectra indicate that, at room temperature, the electronic structures of the two reduction compounds 1˙⁻ and 2˙⁻ are quite different. In 1˙⁻, in good accordance with DFT predictions, the unpaired electron is delocalized on the full molecule while in 2˙⁻ it is confined on a single phosphaalkene moiety. This difference is attributed to the short distance between the two phenylphosphaalkene groups in 2˙⁻ which hinders their reorientation after addition of an electron. The role of this motion is consistent with the fact that two additional paramagnetic species are detected at 145 K: the dianion 2²⁻ characterized by a rather small exchange coupling constant and the radical monoanion 2*˙⁻ resulting from the formation of a one electron P–P bond. These two species are probably reaction intermediates which can lead to the formation of biphosphane.

The connection of two Cr^III sensitizers around a central Er^III acceptor in a self-assembled cation provides high local metal concentrations that favor efficient nonlinear energy transfer upconversion luminescence (see picture). Upon selective low-energy near-infrared irradiation of Cr^III-centered transitions, 1 displays an unprecedented molecular two-photon upconverted green Er^III-centered emission.

The compound of stoichiometry Mn(II)₃[Mn(III)(CN)₆]₂·zH₂O (z = 12−16) (1) forms air-stable, transparent red crystals. Low-temperature single crystal optical spectroscopy and single crystal X-ray diffraction provide compelling evidence for N-bonded high-spin manganese(II), and C-bonded low-spin manganese(III) ions arranged in a disordered, face-centered cubic lattice analogous to that of Prussian Blue. X-ray and neutron diffraction show structured diffuse scattering indicative of partially correlated (rather than random) substitutions of [Mn(III)(CN)₆] ions by (H₂O)₆ clusters. Magnetic susceptibility measurements and elastic neutron scattering experiments indicate a ferrimagnetic structure below the critical temperature T_c = 35.5 K.