Electronic and structural properties of (n = 3–6) , and

Recently, a new class of free stable gas-phase dianions with general formula Be n - 1 O n 2 - was discovered experimentally and, moreover, a CuBe 2 O 4 2 - dianion as well as an unidentified half-integral m/z signal at 53.5 tentatively assigned to MgBe 2 O 4 2 - were detected. Here, the structural and electronic properties of these dianions are investigated by means of high-level ab initio calculations. It is demonstrated that the Be n - 1 O n 2 - (n ⩾ 4), MgBe 2 O 4 2 - and CuBe 2 O 4 2 - dianions exhibit linear geometries and represent electronically stable dianions in the gas phase. Relations of these dianions to other known free stable dianions are discussed.