A metastable brominated nanodiamond surface enables room temperature and catalysis-free amine chemistry

Cynthia  Melendrez; Jorge Lopez-Rosas; Camron Stokes; Tsz Cheung; Sang-Jun Lee; Charles Titus; Jocelyn Valenzuela; Grace Jeanpierre; Halim Muhammad; Polo Tran; Perla Sandoval; Tyanna Supreme; Virginia Altoe; Jan Vavra; Helena Raabova; Vaclav Vanek; Sami Sainio; William Doriese; Galen O'Neil; Daniel Swetz; Joel Ullom; Kent Irwin; Dennis Nordlund; Petr Cigler; Abraham Wolcott

doi:10.26434/chemrxiv-2022-xzxmr

Nanoscience

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A metastable brominated nanodiamond surface enables room temperature and catalysis-free amine chemistry

Working Paper

Cynthia Melendrez San Jose State University ,
Jorge Lopez-Rosas San Jose State University ,
Camron Stokes San Jose State University ,
Tsz Cheung San Jose State University ,
Sang-Jun Lee SLAC National Accelerator Laboratory ,
Charles Titus Stanford University ,
Jocelyn Valenzuela San Jose State University ,
Grace Jeanpierre San Jose State University ,
Halim Muhammad San Jose State University ,
Polo Tran San Jose State University ,
Perla Sandoval San Jose State University ,
Tyanna Supreme San Jose State University ,
Virginia Altoe Lawrence Berkeley National Laboratory ,
Jan Vavra Institute of Organic Chemistry and Biochemistry ,
Helena Raabova Institute of Organic Chemistry and Biochemistry ,
Vaclav Vanek Institute of Organic Chemistry and Biochemistry ,
Sami Sainio University of Oulu ,
William Doriese National Institute of Standards and Technology ,
Galen O'Neil National Institute of Standards and Technology ,
Daniel Swetz National Institute of Standards and Technology ,
Joel Ullom National Institute of Standards and Technology ,
Kent Irwin Stanford University ,
Dennis Nordlund SLAC National Accelerator Laboratory ,
Petr Cigler Institute of Organic Chemistry and Biochemistry ,
Abraham Wolcott San Jose State University

Abstract

Bromination of high-pressure high-temperature (HPHT) nanodiamond (ND) surfaces has not been explored and can open new avenues for increased chemical reactivity and diamond lattice covalent bond formation. The large bond dissociation energy of the diamond lattice-oxygen bond is a challenge that prevents new bonds from forming and most researchers simply use oxygen-terminated ND (alcohols and acids) as a reactive species. In this work, we transformed a tertiary alcohol-rich ND surface to an amine surface with 50% surface coverage and was limited by the initial rate of bromination. We observed that alkyl-bromide moieties are highly labile on NDs and are metastable as previously found using density functional theory. The instability of the bromine terminated ND is explained by steric hindrance and poor surface energy stabilization. The strong leaving group properties of the alkyl-bromide intermediate were found to form diamond-nitrogen bonds at room temperature and without catalysts. The chemical lability of the brominated ND surface led to efficient amination with NH3•THF at 298 K, and a catalyst-free Sonogashira-type reaction with an alkyne-amine produced an 11-fold increase in amination rate. Overlapping spectroscopies under inert, temperature-dependent and open-air conditions provided unambiguous chemical assignments. Amine-terminated NDs and folic acid were conjugated using sulfo-NHS/EDC coupling reagents to form amide bonds, confirming that standard amine chemistry remains viable. This work supports that a robust pathway exists to activate a chemically inert diamond surface at room temperature, which broadens the pathways of bond formation when a reactive alkyl-bromide surface is prepared. The unique surface properties of brominated and aminated nanodiamond reported here are impactful to researchers who wish to chemically tune diamond for quantum sensing applications or as an electron source for chemical transformations.