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. 2022 Jul 29;38(31):9697–9707. doi: 10.1021/acs.langmuir.2c01391

Figure 6.

Figure 6

(a) Area per molecule and (b) minimum surface tension as a function of the length of the alkyl chain n for the two types of counterions. The area per molecule is the value at the collapse Acol for the RuCn(PF6)2 compounds (Table 1) and the excluded area α from the Volmer model for the RuCn(Cl)2 compounds (Table 3). The scale of corresponding intermolecular distance d is shown on the right axis. (b) The minimum surface tension corresponds to the surface tension at the collapse γcol for the RuCn(PF6)2 compounds and to the minimum equilibrium surface tension γmin for the RuCn(Cl)2 compounds. (c) DFT-minimized molecular geometry of RuC172+ in the gas phase showing the dimensions of the ruthenium head. (d) Hypothesized arrangements of the bis-cationic amphiphiles at the air–water interface.