Is o-carborane photoluminescent?

At 77 K in the solid state and in ethanol glasses, o-carborane (1,2-C2B10H12) shows a relatively intense (ϕ ∼ 10−3 at λexc = 260 nm) structured photoluminescence (λmax = 441 nm).In agreement with the rather slow decay of this emission (τ ∼ 4 s) it is suggested to be a phosphorescence. While it appears to be a genuine property of o-carborane an unknown impurity as origin of this luminescence is not completely excluded.