“…As we expected, at room temperature, solidstate of 1 shows three distinct strong photoluminescence with maxima (λ em at 469 nm, 483 nm and 494 nm) upon excitation at 355 nm ( Figure 7). According to previous research and our investigation on Cu I -tetrazolate compounds, 3,[12][13][14][15]27,28 the two peaks at about 483 nm and 494 nm (shoulder) may be attributed to a [Cu-π*(tetrazolate)] metal-to-ligand charge transfer (MLCT), 19 while another strong peak at about 469 nm in title complex is tentatively probably involved with Cu···Cu [3d-4s] cluster-centered (CC) excited states. Especially, there may exist CC excited states because of the vibronic progression in the spectra and the short Cu···Cu distances in the structures, 25 but it is still uncertain in light of Cotton's work through DFT calculations, which points out that short Cu···Cu separation does not guarantee a metal-metal bond, and related bonds and angles with the bridging ligands should be taken into account.…”