Tristannosumanene-based substituent-defined binding pockets: substituent-dependent fullerene recognition and charge-transport modulation.

Exploiting heavy main-group centers to create three-dimensional binding environments in π-frameworks offers an underexplored strategy for controlling fullerene assembly and electronic function. Herein, we report the first isolable tristannosumanenes, obtained via a one-step multi-site tin insertion into a triphenylene precursor. Single-crystal analysis showed that the tetracoordinate tin centers arrange their exocyclic substituents alternately above and below the π-plane, generating substituent-defined binding pockets whose depth is shifting from 2.1 Å (methyl) to 4.3 Å (phenyl substitution). The methyl-substituted 2a binds C60 in solution with a high association constant (Ka = 6.40 × 105 M-1), whereas DFT calculations reveal that deeper pockets do not enhance intrinsic affinity (ΔE = -0.25 vs. +1.39 kcal mol-1). FP-TRMC measurements showed contrasting photoconductivity trends upon fullerene complexation-suppression for 2a⊃C60 and enhancement for 2b⊃C60-correlated with their divergent packing topologies (Pnma vs. P2/n). These results establish substituent engineering at tetracoordinate tin centers as a practical strategy for altering binding-pocket geometry, fullerene organization, and charge-transport behavior in heterasumanene-based π-systems.