Molecular Programming of Diorganyl Dichalcogenides for Rational Nanocrystal Design

ConspectusSoft-chemistry nanocrystal synthesis leverages low-temperature, solution-phase reactions to access materials that can be kinetically stabilized rather than thermodynamically favored. Under such mild conditions, reaction pathways are governed not only by precursor composition but also by the molecular details that dictate how reactive atomic species are generated and delivered. Harnessing this kinetic sensitivity offers a powerful opportunity: by deliberately programming precursor reactivity, nanocrystal composition, structure, and morphology can be rationally designed rather than empirically discovered.In this Account, we describe how diorganyl dichalcogenides (R-E-E-R; R = Bn, Ph, Me, etc.; E = S, Se, Te) have emerged as a versatile and predictive molecular platform for implementing this concept of molecular programming in the soft-chemistry synthesis of metal chalcogenide nanocrystals. The key design variable in these precursors is the strength of the C-E bond, which can be systematically tuned through the choice of organic substituent (R). This tunability directly governs the kinetics and speciation of chalcogen release, providing molecular-level control over nucleation, growth, and phase evolution.Early applications of diorganyl dichalcogenides demonstrated their broad synthetic utility, enabling access to nanocrystals spanning unary to quaternary compositions and revealing metastable crystal structures inaccessible by conventional high-temperature routes. However, the origins of their phase selectivity initially remained largely empirical. Over the past decade, mechanistic insight has transformed this empirical toolbox into a predictive strategy. We show how the rational selection of R₂E₂ precursors enables deterministic phase control of copper selenide intermediates with distinct anion sublattices, which subsequently act as structural templates for topotactic cation exchange into multinary chalcogenides with targeted polymorphs. Data-driven phase mapping and mechanistic studies collectively establish the precursor bond strength, temperature, and reaction medium as orthogonal levers governing kinetic versus thermodynamic outcomes.More recently, this molecular programming framework has been extended beyond close-packed chalcogenides to include non-close-packed alkali and alkaline earth metal chalcogenides, where large ionic cations reduce framework dimensionality and introduce new polymorphic landscapes. In these systems, diorganyl dichalcogenides enable direct polymorphic control, access to low-dimensional motifs, and the selective stabilization of metastable phases without relying on binary intermediates, highlighting the generality of the approach. Together, these advances establish diorganyl dichalcogenides as a generalizable molecular platform for rational nanocrystal design, demonstrating how precursor-level chemical insight can be translated into predictable control over nanocrystal synthesis. By integrating a mechanistic understanding with molecular design, this approach offers a blueprint for expanding accessible material spaces and for uncovering new metastable compositions, structures, and functionalities through soft-chemistry routes.