  We study the stability of the different quark substructures in a quark
cluster approach to pentaquark states considering the color-magnetic spin-spin
interactions between quarks. The most likely configuration is found to be a
triquark-diquark one where the two quarks of the diquark are coupled to spin
zero and anti-triplet representations of flavor and color, and the triquark has
spin one-half and belongs to the triplet representation of color and to
anti-sextet of flavor. To ensure total antisymmetry under the interchange of
identical particles, triquark and diquark are in relative p-wave. Using this
configuration we estimate the masses and magnetic moments of pentaquarks.
Finally the calculation of the masses has been extended to some charmed
pentaquarks.
