Anion-pi　interactions　attract　much　interest　in　theory　but　remain　difficult　to　be　seen　at　work.　Naphthalene　diimides　are　ideal　to　study　anion-pi　interactions　because　their　quadrupole　moment　is　exceptionally　positive.　A　known　strategy　to　increase　pi-acidity　is　the　introduction　of　the　electron-withdrawing　groups　into　naphthalene　diimides　through　covalent　bonding.　Here　we　reported　that　such　pi-acidity　could　be　modulated　by　a　non-covalent　approach.　The　incorporation　of　an　anionic　phenolate　substituent　into　the　naphthalene　diimide　core　at　the　peripheral　positions　not　only　yielded　an　unprecedented　NIR　absorption　band　close　to　1000　nm　that　was　assigned　to　the　pronounced　intramolecular　charge　transfer　from　strong　electron-donating　oxide　anion　to　electron-poor　naphthalene　diimide　unit,　but　also　strengthened　the　interplay　between　the　added　anions　and　naphthalene　diimide　acceptors　due　to　the　cooperative　effect　of　the　simultaneous　electrostatic　interactions　between　the　counter　cations　and　phenolate　ions.　(C)　2014　Elsevier　Ltd.　All　rights　reserved.