ic9b01468_si_001.pdf (2.2 MB)
Host–Guest Feature of DPPP Bridged Arene–Ruthenium Clip Derived Molecular Rectangle
journal contribution
posted on 2019-07-31, 18:33 authored by Suman Dhara, Mohd. Asif Ansari, Goutam Kumar LahiriThe
development of DPPP2– (H2DPPP = 2,5-dihydro-3,6-di-2-pyridylpyrrolo(3,4-c)pyrrole-1,4-dione) bridged (NN∩NN) diruthenium complexes [(Cym)(X)RuII(μ-dppp)RuII(X)(Cym)] (Cym = para-cymene and X = OTf– (1), SCN– (2), N3– (3), NO2–(4)) are considered as the probable
molecular clips for the construction of metallarectangle. Crystal
structures of 2–4 established anticonfiguration
with respect to monodentate SCN–, N3– and NO2– groups, respectively.
Though molecular clips 2–4 failed
to provide the desired metallarectangle in combination with the 4,4′-bipyridine
spacer, 1 with the labile OTf groups facilitated to achieve
the metallarectangle 5. The crystal structure of 5 revealed that two twisted 4,4′-bipyridine spacers
bridged between the two units of dimeric 1 in symmetric
fashion, which in effect led to the newer class of molecular rectangle 5 with a hydrophobic cavity size of the cationic host of 8.32
× 11.11 Å2. Furthermore, the host–guest
interaction potential of 5 with special reference to
the guest molecule, pyrene, was explored. The crystal structure of
the resultant molecule 6 ascertained the partial encapsulation
of two pyrene molecules inside the hydrophobic cavity of 5, due to the twisted 4,4′-bipyridine spacer units between
the two ruthenium clips. It also attributed a noncovalent CH−π
interaction involving protons of pyrene and the π-electron cloud
of 4,4′-bipyridine as well as a weak interaction between pyrene
protons and the pendant CO group of DPPP. Encapsulation of
the guest molecule (pyrene) inside the cavity of the metallarectangle
was also monitored by following the quenching of florescent intensity
of pyrene on addition of 5.