Nibr2

All-trans retinal, ammonium sulfate, ampicillin, DNase, isopropyl β-d-1-thiogalactopyranoside (IPTG), octyl β-d-1-thioglucoside (OTG), decyl β-d-maltoside (DM), dodecyl β-d-maltoside (DDM), ethanol, imidazole, lysozyme, MgCl₂, 2-(N-morpholino) ethanesulfonic acid, (MES), NaCl, NaN₃, Na citrate, polyethylene glycol 4000 (PEG-4000), FeSO₄, NiBr₂, ZnCl₂, CoSO₄, CdCl_2, 4,4′-dinonyl-2,2′-dipyridyl (Dinonyl) and 4,4′-diphenyl-2,2′-dipyridyl (Diphenyl) were obtained from Sigma-Aldrich (St. Louis, MO).

Chloroform (CHCl₃, ≥99.8%) and DMF (≥99.8%) were obtained from Sigma Aldrich and J.T. Baker, respectively. NiBr₂ (>98.0%) was obtained from Sigma Aldrich. Reagents were used without further purification. 5,5-Dimethyl-1-pyrroline N-oxide (DMPO) (>98.0%) was obtained from Cayman Chemical Co. and used as a spin trap. Glass pressure tubes (Ace Glass, Inc., pressure tubes #15 with a plunger valve, PTFE Bushing and FETFE^® O-Ring, volume 50 ml) were cleaned by immersion in a H₂SO₄/30% H₂O₂ piranha solution (7:3 v/v) for 10 min. Subsequently, they were washed with deionized water and dried in an oven for 24 h at 130 °C. Caution: piranha is an extremely dangerous oxidizing agent and should be handled with care using appropriate personal protection. 1,3,5,7-Tetrakis{4-[(E)-2-pyridin-4-yl-vinyl]phenyl} adamantane (TPVA) was prepared according to a literature procedure^{47 (link)}.