Poly(para-phenylene) possesses extraordinary compressive and tensile strength, low density, excellent radiation resistance and high stability toward oxygen, moisture and temperature. The oligomeric members are insulators in their pristine from but can be converted to highly conducting charge transfer complexes when doped with electron donors or acceptors. Moreover, superconductivities have been demonstrated in potassium doped p-terphenyl, p-quarterphenyl and p-quinquephenyl with Tc’s up to 120 K. For these reasons, p-quinquephenyl (C30H22) has attracted our attention as an interesting new ligand platform for chemical reduction and coordination chemistry studies. Herein we investigated the reduction behavior of p-quinquephenyl with Group 1 metals ranging from Li to Rb. As a result, an extended family of the doubly-reduced p-quinquephenyl anions has been isolated with the corresponding alkali metal countercations and characterized structurally and spectroscopically. The different coordination mode of Na+ ion vs. the heavier Group 1 congeners has been demonstrated. In addition, the Li-induced reduction allowed the isolation of the first “naked” p-quinquephenyl dianion. The X-ray crystallographic study of these organometallic complexes revealed a p-quinquephenyl core deformation, details on metal ion coordination and unique solid-state assemblies. These studies could facilitate a deeper understanding of the alkali-metal doped p-quinquephenyl for practical applications.

Structural and spectroscopic insights into a doubly-reduced oligomeric poly(para-Phenylene) fragment

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