We report the substitutional doping of solid-state spiro-bis(5-methyl-1,9-oxido-phenalenyl)boron radical ([2](2)B) by co-crystallization of this radical with the corresponding spiro-bis(5-methyl-1,9-oxido-phenalenyl)beryllium compound ([2](2)Be). The pure compounds crystallize in different space groups ([2](2)B, P (1) over bar, Z = 2; [2](2)Be, P2(1)/c, Z = 4) with distinct packing arrangements, yet we are able to isolate crystals of composition [2](2)B((l-x))Be-x, where x = 0-0.59. The phase transition from the P (1) over bar to the P2(1)/c space group occurs at x = 0.1, but the conductivities of the solid solutions are enhanced and the activation energies reduced for values of x = 0-0.25. The molecular packing is driven by the relative concentration of the spin-bearing ([2](2)B) and spin-free ([2](2)Be) molecules in the crystals, and the extended Huckel theory band structures show that the progressive incorporation of spin-free [2](2)Be in the lattice of the [2](2)B radical (overall bandwidth, W = 1.4 eV, in the pure compound) leads to very strong narrowing of the bandwidth, which reaches a minimum at [2](2)Be (W = 0.3 eV). The results provide a graphic picture of the structural transformations undergone by the lattice, and at certain compositions we are able to identify distinct structures for the [2](2)B and [2](2)Be molecules in a single crystalline phase.