1,3-Bis(4-diethylamino-2-hydroxyphenyl)-2,4-dihydroxycyclobutenediylium 1,3-Cyclobutanedione, 2-(4-(diethylamino)-2-hydroxyphenyl)-4-(4-(diethylamino)-3-hydroxyphenyl)- 121496-65-9 Tetraethyl squarate