Revisiting indeno[1,2-b]fluorene by steric promoted synthesis while isolating the second stable 4nπ
Himanshu Sharma1, Nikhil Bhardwaj1, Soumyajit Das1
1Department of Chemistry, Indian Institute of Technology Ropar, Rupnagar, Punjab-140001, India. chmsdas@iitrpr.ac.in.
Abstract:
Described herein are the steric promoted synthesis and characterization of symmetric, unsymmetric, and benzo-extended indeno[1,2-b]fluorenes 1-5, including the isolation of stable 4nπ indeno[2,1-a]fluorene 6. Single-crystal XRD analyses of 5 and 6 gave the unambiguous confirmation of unsymmetrical [1,2-b]IF and [2,1-a]IF motifs, respectively. The different ground state antiaromaticity of 5 and 6 was explained by Gimarc's approach for topological charge destabilization. The electronic properties of unsymmetrical IFs 2-5 mostly lie midway between 1 and its other known symmetrical counterparts.
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