Preferred compounds include Bi oxide, Co oxide, Cu oxide, {HEAD ~ Fe oxide}, Mn oxide, and Pr oxide, and {TAIL ~ optionally Ag oxide} 
Preferred compounds include Bi oxide , Co oxide , Cu oxide , { HEAD ~ Fe oxide } , Mn oxide , and Pr oxide , and { TAIL ~ optionally Ag oxide }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL