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Photoelectron spectroscopy (PES) is combined with theoretical calculations to investigate the electronic and atomic structures of three doped aluminum clusters, MAl12- (M=Li, Cu, and Au). Well-resolved PES spectra have been obtained at two detachment photon energies, 266 nm (4.661 eV) and 193 nm (6.424 eV). Basin-hopping global optimization method in combination with density-functional theory calculations has been used for the structural searches. Good agreement between the measured PES spectra and theoretical simulations helps to identify the global minimum structures. It is found that LiAl12- (C5v) can be viewed as replacing a surface Al atom by Li on an icosahedral Al13-, whereas Cu prefers the central site to form the encapsulated D3d-Cu@Al12-. For AuAl12-(C1), Au also prefers the central site, but severely distorts the Al12- cage due to its large size.