From red to near infra-red OLEDs: the remarkable effect of changing from X = -Cl to -NCS in a cyclometallated [Pt(N[logical and]C[logical and]N)X] complex N[logical and]C[logical and]N = 5-mesityl-1,3-di-(2-pyridyl)benzene

[PtL6X] X = Cl or NCS and L6 = 5-mesityl-1,3-di(2-pyridyl)-benzene display similar luminescence in solution but, in the solid state, the packing of the molecules is different, with short Pt[three dots, centered]Pt interactions for X = NCS, leading to a red-shifted emission band. The effect has been used to generate OLEDs that emit squarely in the NIR region (855 nm).