Patterning of Nanoparticle-Based Aerogels and Xerogels by Inkjet Printing.

Nanoparticle-based voluminous 3D networks with low densities are a unique class of materials and are commonly known as aerogels. Due to the high surface-to-volume ratio, aerogels and xerogels might be suitable materials for applications in different fields, e.g. photocatalysis, catalysis, or sensing. One major difficulty in the handling of nanoparticle-based aerogels and xerogels is the defined patterning of these structures on different substrates and surfaces. The automated manufacturing of nanoparticle-based aerogel- or xerogel-coated electrodes can easily be realized via inkjet printing. The main focus of this work is the implementation of the standard nanoparticle-based gelation process in a commercial inkjet printing system. By simultaneously printing semiconductor nanoparticles and a destabilization agent, a 3D network on a conducting and transparent surface is obtained. First spectro-electrochemical measurements are recorded to investigate the charge-carrier mobility within these 3D semiconductor-based xerogel networks.

Solid-State Hydrogen-Bond Alterations in a [Co2 Fe2 ] Complex with Bifunctional Hydrogen-Bonding Donors.

A hydrogen-bonding donor-acceptor system, [Co2 Fe2 (bpy*)4 (CN)6 (tp*)2 ](PF6 )2 ⋅2ABA⋅4BN⋅2PE (1 solv ), was prepared by co-crystallization of an external stimuli-responsive cyanide-bridged tetranuclear [Co2 Fe2 ] complex and bifunctional hydrogen-bonding donors, p-aminobenzoic acid. Compound 1 solv exhibited a gradual electron-transfer-coupled spin transition (ETCST), and the removal of solvent molecules led to an abrupt thermal ETCST behavior with increased transition temperature. X-ray structural analysis revealed that the modification of ETCST was caused by a significant alteration of a hydrogen-bonding mode between the tetranuclear [Co2 Fe2 ]2+ cations and ABA molecules. Variable temperature IR measurements indicated that the desolvated form, 1 desolv , showed dynamic alteration of hydrogen-bonding interactions coupled with thermal ETCST behavior. These results suggested that the tetranuclear [Co2 Fe2 ] complex shows solid-state modulations of hydrogen-bond strengths by external stimuli.

A Brønsted-Ligand-Based Iron Complex as a Molecular Switch with Five Accessible States.

A mononuclear FeII complex, prepared with a Brønsted diacid ligand, H2 L (H2 L=2-[5-phenyl-1H-pyrazole-3-yl] 6-benzimidazole pyridine), shows switchable physical properties and was isolated in five different electronic states. The spin crossover (SCO) complex, [FeII (H2 L)2 ](BF4 )2 (1A ), exhibits abrupt spin transition at T1/2 =258 K, and treatment with base yields a deprotonated analogue [FeII (HL)2 ] (1B ), which shows gradual SCO above 350 K. A range of FeIII analogues were also characterized. [FeIII (HL)(H2 L)](BF4 )Cl (1C ) has an S=5/2 spin state, while the deprotonated complexes [FeIII (L)(HL)], (1D ), and (TEA)[FeIII (L)2 ], (1E ) exist in the low-spin S=1/2 state. The electronic properties of the five complexes were fully characterized and we demonstrate in situ switching between multiple states in both solution and the solid-state. The versatility of this simple mononuclear system illustrates how proton donor/acceptor ligands can vastly increase the range of accessible states in switchable molecular devices.