Photochromic channel blockers provide a conceptually simple and convenient way to modulate neuronal activity with light. We have recently described a family of azobenzenes that function as tonic blockers of K(v) channels but require UV-A light to unblock and need to be actively switched by toggling between two different wavelengths. We now introduce red-shifted compounds that fully operate in the visible region of the spectrum and quickly turn themselves off in the dark. Furthermore, we have developed a version that does not block effectively in the dark-adapted state, can be switched to a blocking state with blue light, and reverts to the inactive state automatically. Photochromic blockers of this type could be useful for the photopharmacological control of neuronal activity under mild conditions.

Shine and rise! GABAA–receptors are ligand-gated chloride channels that respond to the major inhibitory neurotransmitter of the mammalian central nervous system. Herein, we introduce azobenzene derivatives of propofol that increase GABA-induced currents when irradiated with light and thus function as photochromic potentiators. One of our molecules, AP2, can be employed as a light-dependent general anesthetic in translucent tadpoles.

The most facile route for the formation of 1H-Tetrazole (1, TZ) is the reaction of sodium azide with ammonium chloride and orthoethyl formate in glacial acetic acid. 1 was deprotonated using alkali hydroxides and carbonates yielding the corresponding metal salts LiTZ (4), NaTZ · H 2 O (5), KTZ (6), RbTZ (7) and CsTZ (8). The nitrogen rich salts NH 4 TZ · H 2 O (2) and N 2 H 5 TZ (3) were synthesized by the reaction of 1H-tetrazole with aqueous NH 3 and N 2 H 4 solutions, respectively. In addition, Sr(TZ) 2 · 5H 2 O (9) was obtained by deprotonation of 1 using Sr(OH) 2 · 8H 2 O and its use as possible energetic ingredient in modern pyrotechnic compositions as a red component was investigated. All compounds were characterized using vibrational (IR and Raman) spectroscopy, multinuclear ( 1 H, 7 Li, 13 C, 14 N, 15 N) NMR spectroscopy and elemental analysis. The structures in the crystalline state of compounds 2, 3, 4, 5, 6, 7, 8 and 9 were determined using low temperature X-ray diffraction and a detailed description is given in this work. The physico-chemical properties of all compounds were investigated using DSC (differential scanning calorimetry) and the heats of formation were calculated using heats of combustion obtained by bomb calorimetry. Since tetrazoles often are energetic Scheme 1 Synthesis of 1H-Tetrazole 1H-Tetrazole is an endothermic compound (ΔH f ϭ 237 kJ mol Ϫ1 ) [11], and therefore its use as an energetic material in propellant systems is discussed. Modern High-Energy Density Materials (HEDM) [12] derive most of their energy either (a) from oxidation of the carbon backbone (traditional energetic materials) [13], or (b) from their high positive heats of formation. Examples for the first class are explosives such as TNT, RDX and HMX. Modern nitro compounds such as CL -20 [14], TEX [15] or the hepta-and octanitrocubanes [16] possess very high densities and have enhanced energetic properties due to their substantial cage strain. For high explosive applications, 1 possesses too low density (ρ ϭ 1.53 g cm Ϫ3 ) and a low decomposition temperature at 188°C. However, the second problem can be improved by deprotonation, which results in higher thermal stability. The strontium salt 9 for example, is stable up to temperatures of 335°C. In this work, several salts of 1Htetrazole are presented including the ammonium and hydrazinium salts as compounds with high nitrogen contents. The properties of the latter two which determine suitability for use in energetic compositions were investigated, and since modern, smokeless pyrotechnic mixtures could contain alkali and alkaline earth metal salts, several corresponding metal tetrazole salts are also presented in this work. Results and DiscussionSynthesis 1 was obtained by the reaction of ammonium chloride, triethyl orthoformate and sodium azide in concentrated acetic acid at 80°C for 6h (Scheme 2), followed by recrystallization from ethyl acetate. Salts 2Ϫ9 were obtained by deprotonation of 1 using the bases indicated in Scheme 3. All salts were recrystallized from wat...