Abstract
Reaction of [NiCl(2) (PnH)(4) ] (1) (PnH=6-tert-butyl-pyridazine-3-thione) with NiCl(2) affords the binuclear paddlewheel (PW) complex [Ni(2) (Pn)(4) ] (2). Diamagnetic complex 2 is the first example of a PW complex capable of reversibly binding and releasing NH(3) . The NH(3) ligand in [Ni(2) (Pn)(4) (NH(3) )] (2⋅NH(3) ) enforces major spectroscopic and magnetic susceptibility changes, thus displaying vapochromic properties (λ(max) (2)=532 nm, λ(max) (2⋅NH(3) )=518 nm) and magnetochemical switching (2: S=0; 2⋅NH(3) : S=1). Upon repeated adsorption/desorption cycles of NH(3) the PW core remains intact. Compound 2 can be embedded into thin polyurethane films (2(P) ) under retention of its sensing abilities. Therefore, 2 qualifies as reversible optical probe for ammonia. The magnetochemical switching of 2 and 2⋅NH(3) was studied in detail by SQUID measurements showing that in 2⋅NH(3) , solely the Ni atom coordinated the NH(3) molecule is responsible for the paramagnetic behavior.