The structural, energetic, electronic, and magnetic properties of a series of vanadium naphthalene (Vn-1Npn) sandwich clusters (SWCs) and the VNp sandwich nanowire (SWN) were investigated by means of density functional theory computations. In the energetically most preferred configuration of each Vn-1Npn SWC and SWN, the two nearest-neighbor Np rings form a 45 degrees rotation angle, the two second-nearest-neighbor Np rings are parallel to each other, and V atoms align in a zigzag chain. The local magnetic moments in Vn-1Npn SWCs favor antiferromagnetic coupling due to the superexchange mechanism. Especially, both electron and hole injection can switch Vn-1Npn SWCs and VNp SWN from the antiferromagnetic state to the ferromagnetic state, thus manipulating the magnetization direction. These results suggest the potential applications of Vn-1Npn SWCs and VNp SWN in spintronics.