A compound of formula: or a pharmaceutically acceptable salt or ester thereof, wherein: Q is piperazine-1,4-diyl; 2,5-diazabicyclo[2.2.1]heptane-2,5-diyl; 2,5-diazabicyclo[2.2.2]octane-2,5-diyl; 1,4-diazepane-1,4-diyl; benzene-1,4-diamine-N 1,N 4 -diyl; ethane-1,2-diamine-N 1,N 2 -diyl; N 1,N 2 -dialkylethane-1,2-diamine-N 1,N 2 -diyl; propane-1,3-diamine-N 1,N 3 -diyl; N 1,N 3 -dialkylpropane-1,3-diamine-N 1,N 3 -diyl; 1,4-diaminoanthracene-9,10-dione-1,4-diyl; C 6 arene-1,4-diamine-N 1,N 4 -diyl wherein the arene is substituted with one to four substituents in the 2, 3, 5, or 6 positions and wherein the substituents are independently selected from the group consisting of -C O(C 1 to C 6)alkyl, OH, O(C 1 to C 6)alkyl, (C 1 to C 6)alkyl, CF 3, F, Cl, and Br; or substituted piperazine-1,4-diyl wherein the piperazine is substituted with one to eight substituents in the 2, 3, 5, or 6 positions and wherein the substituents are independently selected from the group consisting of (C 1 to C 6)alkyl, aryl, aryl(C 1 to C 6)alkyl, C OH, and C O(C 1 to C 6)alkyl; A 1 and A 1 ' are each independently N or CR 6; A 2 and A 2 ' are each independently N or CR 7; A 3 is NR 8; A 3 ' is NR 8, O, or S; A 4 and A 4 ' are each independently N or CR 9; A 5 and A 5 ' are each independently N or CR 10; A 6 and A 6 ' are each independently N or CR 11; and R 1, R 1', R 2, R 2', R 3, R 3', R 4, R 4', R 6, R 7, R 8, R 9, R 10, and R 11, if present, are in each instance independently selected from the group consisting of hydrogen, alkyl, halo, trifluoromethyl, dialkylamino wherein each alkyl is the same or different, -NH 2, alkylamino, and arylalkyl. Q is piperazine-1,4-diyl; 2,5-diazabicyclo[2.2.1]heptane-2,5-diyl; 2,5-diazabicyclo[2.2.2]octane-2,5-diyl; 1,4-diazepane-1,4-diyl; benzene-1,4-diamine-N 1,N 4 -diyl; ethane-1,2-diamine-N 1,N 2 -diyl; N 1,N 2 -dialkylethane-1,2-diamine-N 1,N 2 -diyl; propane-1,3-diamine-N 1,N 3 -diyl; N 1,N 3 -dialkylpropane-1,3-diamine-N 1,N 3 -diyl; 1,4-diaminoanthracene-9,10-dione-1,4-diyl; C 6 arene-1,4-diamine-N 1,N 4 -diyl wherein the arene is substituted with one to four substituents in the 2, 3, 5, or 6 positions and wherein the substituents are independently selected from the group consisting of -C O(C 1 to C 6)alkyl, OH, O(C 1 to C 6)alkyl, (C 1 to C 6)alkyl, CF 3, F, Cl, and Br; or substituted piperazine-1,4-diyl wherein the piperazine is substituted with one to eight substituents in the 2, 3, 5, or 6 positions and wherein the substituents are independently selected from the group consisting of (C 1 to C 6)alkyl, aryl, aryl(C 1 to C 6)alkyl, C OH, and C O(C 1 to C 6)alkyl; A 1 and A 1 ' are each independently N or CR 6; A 2 and A 2 ' are each independently N or CR 7; A 3 is NR 8; A 3 ' is NR 8, O, or S; A 4 and A 4 ' are each independently N or CR 9; A 5 and A 5 ' are each independently N or CR 10; A 6 and A 6 ' are each independently N or CR 11; and R 1, R 1', R 2, R 2', R 3, R 3', R 4, R 4', R 6, R 7, R 8, R 9, R 10, and R 11, if present, are in each instance independently selected from the group consisting of hydrogen, alkyl, halo, trifluoromethyl, dialkylamino wherein each alkyl is the same or different, -NH 2, alkylamino, and arylalkyl.