Controlling
the self-assembly of molecules on solid surfaces is
of great importance for creating new functional nanostructures. In
this work, phase transitions in the self-assembled structure of the
1,3,5-tris(3-carboxyphenyl)benzene (mTCPB) molecule on the Ag(111)
surface at different annealing temperatures are characterized by ultrahigh
vacuum scanning tunneling microscopy, which reflects the different
deprotonation levels of the mTCPB molecule. We also demonstrate that
the two-dimensional chirality of the precursor is a powerful tool
for steering the supramolecular structures on surfaces.
The on-surface reaction processes of 1,4-dibromo-2,5-diiodobenzene
(C6H2Br2I2) on Au(111)
and Ag(100) were systematically investigated under ultra-high vacuum
conditions by using scanning tunneling microscopy. Deiodination underwent
at RT on both surfaces with the formation of organometallic intermediates
connected by C–Au–C and C–Ag–C linkages.
In particular, partial deiodination on Au(111) resulted in self-assembled
ordered structures of organometallic trans-trimers, which were converted
into longer organometallic chains after complete deiodination at 100
°C. On Ag(100), complete deiodination gave rise to disordered
molecular clusters at RT and organometallic intermediates were formed
via the debromination process after annealing to 150 °C. Further
annealing to higher temperatures resulted in covalent C–C bonded
polyphenylene chains and finally disordered graphene nanostructures
via cyclodehydrogenation. Our study provides fundamental comprehension
of temperature-selective on-surface dehalogenation reactions of multi-halogen-substituted
precursors for constructing designer covalently bonded networks.
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