Structure transformation from Sierpiński triangles to chains assisted by gas molecules
Chao Li, Zhen Xu, Yajie Zhang, Jie Li, Na Xue, Ruoning Li, Mingjun Zhong, Tianhao Wu, Yifan Wang, Yifan Wang, Na Li, Ziyong Shen, Shimin Hou, Richard Berndt, Yongfeng Wang, Yongfeng Wang, Song Gao
Abstract
ABSTRACT Reversible transformations between fractals and periodic structures are of fundamental importance for understanding the formation mechanism of fractals. Currently, it is still a challenge to controllably achieve such a transformation. We investigate the effect of CO and CO2 molecules on Sierpiński triangles (STs) assembled from Fe atoms and 4,4″-dicyano-1,1′:3′,1″-terphenyl (C3PC) molecules on Au surfaces. Using scanning tunneling microscopy, we discover that the gas molecules induce a transition from STs into 1D chains. Based on density functional theory modeling, we propose that the atomistic mechanism involves the transformation of a stable 3-fold coordination Fe(C3PC)3 motif to Fe(C3PC)4 with an axially bonded CO molecule. CO2 causes the structural transformation through a molecular catassembly process.