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New quadrupolar fluorophores that exhibit enhanced twophoton excited fluorescence were designed according to a molecular engineering approach based on push-push and pull-pull elongated molecules built from a rigid conjugated core (either dihydrophenanthrene or dithienothiophene).

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Reduction of the uranium(IV) thiolates Cp* 2 U(SR) 2 (Cp* ) η-C 5 Me 5 , R ) Ph, Me, i Pr or t Bu) with sodium amalgam afforded the corresponding U(III) complexes Na[Cp* 2 U(SR) 2 ] (R ) Ph, 2a; Me, 2b; i Pr, 2c) or the U(IV) sulfide Na[Cp* 2 U(S t Bu)(S)]. C-S bond cleavage of a thiolate ligand was also observed during the thermal decomposition of 2c into the sulfide Na[Cp* 2 U(S i Pr)(S)], whereas 2b was transformed in refluxing THF into the thiametallacyclopropane complex Na[Cp* 2 U(SMe)(SCH 2 )], resulting from C-H bond activation of a SMe group. The X-ray crystal structures of [Na(18-crown-6)(THF) 2 ][Cp* 2 U(S i Pr) 2 ], [Na(18-crown-6)][Cp* 2 U(S t Bu)(S)], and [Na(18-crown-6)(THF) 2 ][Cp* 2 U(SMe)(SCH 2 )] have been determined.