What Stabilizes the LinPn Inorganic Double Helices?

Recently, inorganic double-helical structures based on simple lithium and phosphorus salts have been demonstrated. We have analyzed the nature of bonding in these double helices of LinPn (n = 7-9). Similar to DNA, noncovalent interactions and cooperativity play an important role in stabilizing the inorganic double helices. Cooperativity imparts an additional stabilization of 4.5 to 10.1 kcal/mol per Li-P pair. In addition, the ionicity of Li-P units further augments the stability of these inorganic double-helix structures in contrast with the canonical base pairs in DNA, where noncovalent interactions determine the duplex stability. Unwinding is shown to be unfavorable, and cleavage of a few edge Li-P bonds leads to spontaneous self-healing into the intact double-helix tract.