Synthesis of Highly Fluorescent BODIPY-Based Nanocars

The convergent synthesis of inherently highly fluorescent nanocars incorporating 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY)-containing axles and p-carborane wheels is reported. These nanocars are expected to exhibit rolling motion with predetermined patterns over smooth surfaces, depending on their chassis. Their quantum yields of fluorescence (ΦF > 0.7) make them excellent candidates for imaging and tracking by single-molecule fluorescence microscopy. An analogue as a stationary control with tert-butyl groups instead of p-carborane wheels was also synthesized

Toward Chemical Propulsion: Synthesis of ROMP-Propelled Nanocars

The synthesis and ring-opening metathesis polymerization (ROMP) activity of two nanocars functionalized with an olefin metathesis catalyst is reported. The nanocars were attached to a Hoveyda−Grubbs first- or second-generation metathesis catalyst via a benzylidene moiety. The catalytic activity of these nanocars toward ROMP of 1,5-cyclooctadiene was similar to that of their parent catalysts. The activity of the Hoveyda−Grubbs first-generation catalyst-functionalized nanocar was further tested with polymerization of norbornene. Hence, the prospect is heightened for a ROMP process to propel nanocars across a surface by providing the translational force

Influence of the Substrate on the Mobility of Individual Nanocars

We monitored the mobility of individual fluorescent nanocars on three surfaces: plasma cleaned, reactive ion etched, and amine-functionalized glass. Using single-molecule fluorescence imaging, the percentage of moving nanocars and their diffusion constants were determined for each substrate. We found that the nanocar mobility decreased with increasing surface roughness and increasing surface interaction strength

Spiro-Aziridine and Bislactam Formation from Bisketene−Imine Cycloadditions

1,2-Bisketenes 6 react with imines PhCHNAr, (E)-2, forming spiro-aziridines 7. DFT computations indicate that this occurs by nucleophilic attack of the imine on the carbonyl carbon of the more reactive arylketene moiety, followed by cyclization, and not by prior cyclization of the 1,2-bisketene forming a carbene lactone intermediate. Computations also indicate that the previously studied bisketene 10 from benzocyclobutadiene 9 is 4.0 kcal/mol less stable than carbene lactone 12 that would result from cyclization but that the failure to observe 12 results from a lower barrier for 10 to instead revert to 9. 1,2-, 1,3-, and 1,4-Bisketenylbenzenes 16, 19, and 22 react with imines forming bis(β-lactams), with a preference for formation of mixtures of trans, trans chiral (±) and achiral diastereomeric products

Spiro-Aziridine and Bislactam Formation from Bisketene−Imine Cycloadditions

1,2-Bisketenes 6 react with imines PhCHNAr, (E)-2, forming spiro-aziridines 7. DFT computations indicate that this occurs by nucleophilic attack of the imine on the carbonyl carbon of the more reactive arylketene moiety, followed by cyclization, and not by prior cyclization of the 1,2-bisketene forming a carbene lactone intermediate. Computations also indicate that the previously studied bisketene 10 from benzocyclobutadiene 9 is 4.0 kcal/mol less stable than carbene lactone 12 that would result from cyclization but that the failure to observe 12 results from a lower barrier for 10 to instead revert to 9. 1,2-, 1,3-, and 1,4-Bisketenylbenzenes 16, 19, and 22 react with imines forming bis(β-lactams), with a preference for formation of mixtures of trans, trans chiral (±) and achiral diastereomeric products

Spiro-Aziridine and Bislactam Formation from Bisketene−Imine Cycloadditions

1,2-Bisketenes 6 react with imines PhCHNAr, (E)-2, forming spiro-aziridines 7. DFT computations indicate that this occurs by nucleophilic attack of the imine on the carbonyl carbon of the more reactive arylketene moiety, followed by cyclization, and not by prior cyclization of the 1,2-bisketene forming a carbene lactone intermediate. Computations also indicate that the previously studied bisketene 10 from benzocyclobutadiene 9 is 4.0 kcal/mol less stable than carbene lactone 12 that would result from cyclization but that the failure to observe 12 results from a lower barrier for 10 to instead revert to 9. 1,2-, 1,3-, and 1,4-Bisketenylbenzenes 16, 19, and 22 react with imines forming bis(β-lactams), with a preference for formation of mixtures of trans, trans chiral (±) and achiral diastereomeric products

Spiro-Aziridine and Bislactam Formation from Bisketene−Imine Cycloadditions

1,2-Bisketenes 6 react with imines PhCHNAr, (E)-2, forming spiro-aziridines 7. DFT computations indicate that this occurs by nucleophilic attack of the imine on the carbonyl carbon of the more reactive arylketene moiety, followed by cyclization, and not by prior cyclization of the 1,2-bisketene forming a carbene lactone intermediate. Computations also indicate that the previously studied bisketene 10 from benzocyclobutadiene 9 is 4.0 kcal/mol less stable than carbene lactone 12 that would result from cyclization but that the failure to observe 12 results from a lower barrier for 10 to instead revert to 9. 1,2-, 1,3-, and 1,4-Bisketenylbenzenes 16, 19, and 22 react with imines forming bis(β-lactams), with a preference for formation of mixtures of trans, trans chiral (±) and achiral diastereomeric products

Spiro-Aziridine and Bislactam Formation from Bisketene−Imine Cycloadditions

1,2-Bisketenes 6 react with imines PhCHNAr, (E)-2, forming spiro-aziridines 7. DFT computations indicate that this occurs by nucleophilic attack of the imine on the carbonyl carbon of the more reactive arylketene moiety, followed by cyclization, and not by prior cyclization of the 1,2-bisketene forming a carbene lactone intermediate. Computations also indicate that the previously studied bisketene 10 from benzocyclobutadiene 9 is 4.0 kcal/mol less stable than carbene lactone 12 that would result from cyclization but that the failure to observe 12 results from a lower barrier for 10 to instead revert to 9. 1,2-, 1,3-, and 1,4-Bisketenylbenzenes 16, 19, and 22 react with imines forming bis(β-lactams), with a preference for formation of mixtures of trans, trans chiral (±) and achiral diastereomeric products

Spiro-Aziridine and Bislactam Formation from Bisketene−Imine Cycloadditions

1,2-Bisketenes 6 react with imines PhCHNAr, (E)-2, forming spiro-aziridines 7. DFT computations indicate that this occurs by nucleophilic attack of the imine on the carbonyl carbon of the more reactive arylketene moiety, followed by cyclization, and not by prior cyclization of the 1,2-bisketene forming a carbene lactone intermediate. Computations also indicate that the previously studied bisketene 10 from benzocyclobutadiene 9 is 4.0 kcal/mol less stable than carbene lactone 12 that would result from cyclization but that the failure to observe 12 results from a lower barrier for 10 to instead revert to 9. 1,2-, 1,3-, and 1,4-Bisketenylbenzenes 16, 19, and 22 react with imines forming bis(β-lactams), with a preference for formation of mixtures of trans, trans chiral (±) and achiral diastereomeric products

Synthesis of Fluorescent Dye-Tagged Nanomachines for Single-Molecule Fluorescence Spectroscopy

In an effort to elucidate the mechanism of movement of nanovehicles on nonconducting surfaces, the synthesis and optical properties of five fluorescently tagged nanocars are reported. The nanocars were specifically designed for studies by single-molecule fluorescence spectroscopy and bear a tetramethylrhodamine isothiocyanate fluorescent tag for excitation at 532 nm. The molecules were designed such that the arrangement of their molecular axles and p-carborane wheels relative to the chassis would be conducive to the control of directionality in the motion of these nanovehicles