Synthesis, characterization, and UV-vis linear absorption of centrosymmetric pi-systems incorporating closo-dodecaborate clusters

Single- and multibranched centrosymmetric derivatives incorporating B12 clusters B12H11-N(H)=C(H)-C6H4-C6H4-C(H)=(H)N-B12H11]2- (3) and 1,3,5-(4-(B12H11-N(H)=C(H))-C6H4)-C6H3]3- (5) have been synthesized. Both derivatives were characterized by multinuclear NMR and ESI-MS analyses. To the best of our knowledge, compound 5 is the first example of a multicage derivative bearing three B12 units. Compounds 3 and 5 are only slightly yellowish colored. The UV-vis absorption curves of 3 and 5 show intense absorption bands at 360 and 314 nm, respectively. This result permits us to confirm the strong donor effect of the B12 cluster. The hypsochrome effect observed for compound 5 compared to that of compound 3 confirms the interest in multibranched derivatives for the preparation of two-photon absorption materials active in the visible range.