Ionic liquids (ILs) are promising pretreatment solvents for lignocellulosic biomass, but are largely prepared from petroleum precursors. Benzaldehydes from depolymerized lignin, such as vanillin, syringaldehyde, and 4-methoxy benzaldehyde, represent renewable feedstocks for the synthesis of ionic liquids. We herein report syntheses of novel lignin-derived ionic liquids, with extended <
em>
N<
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-alkyl chains, and examine their melting points, cellulose dissolution capacities, and toxicity profiles against <
em>
Daphnia magna<
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and <
em>
E. coli<
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strain 1A1. The latter organism has been engineered to produce isoprenol, a drop-in biofuel and precursor for commodity chemicals. The new <
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N,N<
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-diethyl and <
em>
N,N<
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-dipropyl methyl benzylammonium ILs were liquids at room temperature, showing 75?100 �C decreased melting points as compared to their <
em>
N,N,N<
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-trimethyl benzylammonium analog. Extension of <
em>
N<
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-alkyl chains also increased antibacterial activity threefold, while ionic liquids prepared from vanillin showed 2- to 4-fold lower toxicity as compared to those prepared from syringaldehyde and 4-methoxybenzaldehyde. The trend of antibacterial activity for anions of lignin-derived ILs was found to be methanesulfonate <
acetate <
hydroxide. Microcrystalline cellulose dissolution, from 2 to 4 wt% after 20 min at 100 �C, was observed in all new ILs using light microscopy and IR spectroscopy. Ionic liquids prepared from H-, S- and G-lignin oxidation products provided differential cytotoxic activity against <
em>
E. coli<
/em>
and <
em>
D. magna<
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, suggesting these compounds could be tailored for application specificity within a biorefinery.