The synthesis of the bulky divalent (polyphenylcyclopentadienyl)lanthanoid sandwich complexes [Ln(C 5 Ph 5 ) 2 ] (Ln = Sm, Eu) and [Ln(C 5 Ph 4 H) 2 (solv)] (Ln = Sm, solv = thf; Ln = Eu, solv = dme)], from redoxtransmetalation/protolysis (RTP) reactions, has been achieved. An analogous reaction with Yb afforded the solvent-separated ion pair [Yb(dme) 4 ][C 5 Ph 4 H] 2 . In addition, rare divalent samarium halide complexes [Sm(C 5 Ph 5 )(μ-Br)(thf) 2 ] 2 and [Sm(C 5 Ph 4 H)I(thf) 3 ], were also prepared, either by RTP or ligand rearrangement. X-ray studies showed that the [Ln(C 5 Ph 5 ) 2 ] complexes adopt highly symmetrical sandwich structures, whereas the [Ln(C 5 Ph 4 H) 2 (solv)] complexes have open sandwich structures. The unexpected, but limited, solubility of the [Ln(C 5 Ph 5 ) 2 ] complexes allowed for variabletemperature NMR spectra of [Sm(C 5 Ph 5 ) 2 ] to be obtained. Detailed 1D and 2D NMR studies were conducted on [Sm(C 5 Ph 4 H) 2 (thf)] to ascertain its structure in donor and nondonor solvents. During the course of these studies, the mixed tetraarylcyclopentadienyl sandwich complex [Sm{C 5 (2,5-Ph) 2 (3,4-p-tol 2 )H} 2 (thf)] was also prepared in order to fully assign the spectrum of [Sm(C 5 Ph 4 H) 2 (thf)]. The europium sandwich complexes [Eu(C 5 Ph 5 ) 2 ] and [Eu(C 5 Ph 4 H) 2 (dme)] exhibit remarkable luminescence properties with high quantum yields (45% and 41%, respectively) coupled w i th long emission lifetimes (approximately 800 and 1300 ns, respectively) in toluene.

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Robust methodology to install amide, carbamate, urea and sulfonamide functionality to the 1,8-naphthalimide scaffold has been developed and exemplified. New benzamidonaphthalimide 6, synthesised using this approach, was found to be sensitive to base whereupon fluorescence emission strongly increases (>10-fold) and red-shifts (>4000 cm). The optical properties of deprotonated 6 allow for single molecule fluorescence detection, the first example of such behaviour from this class of fluorophore.