The formation relationship between colloidal magic-size clusters (MSCs) and conventional quantum dots (QDs) has not been well established. Here, we report our systematic study on their formation pathways, using cadmium sulfide (CdS) as a model system. Two Cd precursors were prepared from CdO with branched 2-methyloctadecanoic acid (CHCH(CH)-COOH) and linear oleic acid (CHCH-COOH), reacting with elemental S powder in 1-octadecene (ODE). We show that the presence of MSC-311 (exhibiting a sharp absorption peaking at 311 nm) is regulated by the growth of conventional QDs. We demonstrate that MSC-311 cannot directly convert into conventional QDs but to its immediate precursor (IP-311), which is transparent in optical absorption (>310 nm). We propose that there are two individual pathways for the formation of MSCs and conventional QDs, linked by an intrinsic pathway from MSCs to IPs to fragments to QDs. The present study introduces new avenues to precisely control their formation.

Little is known about the formation pathway of colloidal semiconductor magic‐size clusters (MSCs). Here, the synthesis of the first single‐ensemble ZnSe MSCs, which exhibit a sharp optical absorption singlet peaking at 299 nm, is reported; their formation is independent of Zn and Se precursors used. It is proposed that the formation of MSCs starts with precursor self‐assembly followed by Zn and Se covalent bond formation to result in immediate precursors (IPs) which can transform into the MSCs. It is demonstrated that the IPs in cyclohexane appear transparent in optical absorption, and become visible as MSCs exhibiting one sharp optical absorption peak when a primary amine is added at room temperature. It is shown that when the preparation of the IP is controlled to be within the induction period, which occurs prior to nucleation and growth of conventional quantum dots (QDs), the resulting MSCs can be produced without the complication of the simultaneous coproduction of conventional QDs. The present study reveals the existence of precursor self‐assembly which leads to the formation of colloidal semiconductor MSCs and provides insights into a multistep nucleation process in cluster science.

Alloy semiconductor magic-size clusters (MSCs) have received scant attention and little is known about their formation pathway. Here, we report the synthesis of alloy CdTeSe MSC-399 (exhibiting sharp absorption peaking at 399 nm) at room temperature, together with an explanation of its formation pathway. The evolution of MSC-399 at room temperature is detected when two prenucleation-stage samples of binary CdTe and CdSe are mixed, which are transparent in optical absorption. For a reaction consisting of Cd, Te, and Se precursors, no MSC-399 is observed. Synchrotron-based in-situ small angle X-ray scattering (SAXS) suggests that the sizes of the two samples and their mixture are similar. We argue that substitution reactions take place after the two binary samples are mixed, which result in the formation of MSC-399 from its precursor compound (PC-399). The present study provides a room-temperature avenue to engineering alloy MSCs and an in-depth understanding of their probable formation pathway.

Epoxide-opening ether cyclizations are shown to occur on π-acidic aromatic surfaces without the need of additional activating groups and with autocatalytic amplification. Increasing activity with the intrinsic π acidity of benzenes, naphthalenediimides (NDIs) and perylenediimides (PDIs) support that anion−π interactions account for function. Rate enhancements maximize at 270 for anion−π catalysis on fullerenes and at 5100 M–1 for autocatalysis. The occurrence of anion−π autocatalysis is confirmed with increasing initial rates in the presence of additional product. Computational studies on autocatalysis reveal transition state and product forming a hydrogen-bonded noncovalent macrocycle, like holding their hands and dancing on the active π surface, with epoxide opening and nucleophile being activated by anion−π interactions and hydrogen bonds to the product, respectively.

α-Diazoesters were discovered to be good electrophiles in a catalytic asymmetric α-functionalization of ketones for the first time. This reaction also provided a direct and efficient method for C-N bond formation with excellent yields (up to 98%) and enantioselectivities (up to 99% ee) under mild conditions. The application of the electrophilicity of α-diazoesters opens up a novel way to access the diversity of diazo chemistry.