series of heterometallic square complexes with general molecular formula [Er(CO)(3)Re(mu-(pyterpy)(2)M)](4)- (PF6)(8), where M = Fe, Ru, or Os and where pyterpy is 4'-(4"'-pyridyl)-2,2':6',2"-terpyridine were prepared by self-assembly between BrRe(CO)(5) and (pyterpy)(2)M-(PF6)(2). The luminescence properties and host-guest chemistry of the complexes are explored.