While multicenter halogen bonds typically exhibit negative cooperativity in donor-only systems, crystallographic surveys reveal robust hetero-atomic assemblies featuring the 2I & ctdot;I & ctdot;Nu motif (Nu = N, O, S, and C). Here we present a comprehensive theoretical investigation of this bonding pattern to evaluate its intrinsic electronic synergy. We initially performed a systematic density functional theory (DFT) analysis on fully optimized model systems involving diatomic iodine (I2) and the iodine trimer ((I2)3) acting as sigma-hole donors, interacting with a series of small, linear Lewis bases (HF, CO, HCN, OCN-, SCN-, and SeCN-). Our calculations on these optimized models demonstrate that the (I2)3 trimer functions as a significantly stronger sigma-hole donor than the isolated I2 molecule, confirming pronounced positive cooperativity. To validate these findings in the solid state, we extended the analysis to two representative crystal structures: a homotrimeric 2,4,5-triiodoimidazole assembly (UNOMIV) and a cocrystal of 1,3,5-triiodo-2,4,6-trifluorobenzene with 1,4-dithiane (ZAQZOK). Energy decomposition analysis and quantum theory of atoms in molecules results for these crystallographic systems mirror the trends observed in the model complexes. Specifically, the formation of flanking I & ctdot;I contacts amplifies the sigma-hole depth of the central iodine atom, increasing it from 21.9 to 24.8 kcal mol-1 in UNOMIV and from 30.1 to 33.9 kcal mol-1 in ZAQZOK. Natural bond orbital analysis confirms that charge transfer from the central iodine's lone pairs to the antibonding sigma* orbitals of the flanking molecules drives this synergistic behavior. These findings validate the chemical chameleon property as a foundation for crystal engineering, establishing the 2I & ctdot;I & ctdot;Nu motif as a robust supramolecular synthon.