## 3 Experimental Section  
Most of the starting materials were obtained commercially and all reagents and solvents used were of analytical grade. Hydrazine sulfate and all anions, in the form of tetrabutylammonium salts (such as (_n_-C\({}_{4}\)H\({}_{9}\))\({}_{4}\)NF, (_n_-C\({}_{4}\)H\({}_{9}\))\({}_{4}\)NCl, (_n_-C\({}_{4}\)H\({}_{9}\))\({}_{4}\)NBr, (_n_-C\({}_{4}\)H\({}_{9}\))\({}_{4}\)NI, (_n_-C\({}_{4}\)H\({}_{9}\))\({}_{4}\)NAcO, (_n_-C\({}_{4}\)H\({}_{9}\))\({}_{4}\)NH\({}_{2}\)PO\({}_{4}\)), were purchased from Aladdin Chemistry Co. Ltd (Shanghai, China), stored in a desiccator under a vacuum containing self-indicating silica, and used without any further purification. Tetra-_n_-butylammonium salts were dried for 24 h in a vacuum with P\({}_{2}\)O\({}_{5}\) at 333 K before using. Dimethyl sulfoxide (DMSO) was distilled _in vacuo_ after being dried with CaH\({}_{2}\). C, H, N elemental analysis was made on Vanio-EL (Heraeus, Hanau, Germany). \({}^{1}\)H NMR spectra was recorded on a Varian Plus-400 MHz Spectrometer  
Figure 6: Selected HOMO (**a**); and LUMO (**b**) distributions of **1**, **2**, **3**, **6** and **11**. (Bruker, Germany). ESI-MS was performed with a LC-MS apparatus (Agilent, Santa Clara, CA, USA). UV-vis spectroscopy titration was made on a Shimadzu UV2550 spectrophotometer (Japan) at 298 K. Fluorometric titration was performed on a Cary Eclipse Fluorescence Spectrophotometer (Agilent, Santa Clara, CA, USA) at 298 K. The binding constant (\(K_{\mathrm{s}}\)) was obtained by non-linear least square calculation method for data fitting. The SEM images were obtained by Quanta TM450 FEI (Agilent, Santa Clara, CA, USA) coating it with Au. The kinds of bacteria were hay bacillus, _Staphylococcus aureus_, colon bacillus, typhoid bacillus, and _Pseudomonas aeruginosa_. Antibacterial activity was determined by filter paper method. The qualitative filter paper was made into small round pieces (\(\Phi\) = 6 mm), used after high pressure sterilization. The filter paper was placed in saline water for 2 h as a reference solution. Under the sterile conditions, the appropriate culture medium (20-25 mL) was dashed into a sterilized Petri and made into a solid plate after solidifying. The prepared bacterial suspension (200 \(\upmu\)L) was poured into the appropriate solid medium using rods with a liquid coating. The filter paper was pasted on the bacterial plate. The essential oils (5 \(\upmu\)L) were added onto each piece of filter paper. Colon bacillus, _Staphylococcus aureus_, hay bacillus, typhoid bacillus, and _Pseudomonas aeruginosa_ were placed in a culture incubator (37 \({}^{\circ}\)C) for 24 h. Then the data of antibacterial circle diameter was the difference between the measured value and reference value. Therefore, the experimental data of antibacterial circle diameter showed the antibacterial activity of various bacteria. Twelve compounds (**1**-**12**) were synthesized according to the route shown in Scheme 1. Substituted methyl benzoate was synthesized according to the literature [34]. Substituted benzoic acid (10 mmol), dissolved in methanol (20 mL) and concentrated sulfuric acid (0.5 mL), was added into the above solution. The above mixture was refluxed for 3 h and then the precipitated solid was obtained. Substituted benzohydrazide was synthesized according to the literature [35,36]. Substituted methyl benzoate (10 mmol), dissolved in methanol and hydrazine hydrate (80%, 2 mL), was added to the solution. Then the mixture was heated under refluxing for 6 h and the precipitate was separated by filtration. The solid was recrystallized using 95% ethanol, washed with diethyl ether, and dried under a vacuum. Benzohydrazide: m.p. 111-114 \({}^{\circ}\)C.  
_p_-Nitrobenzohydrazide: m.p. 214-217 \({}^{\circ}\)C. \({}^{1}\)H NMR (DMSO-_d\({}_{6}\)_): \(\delta\) 10.11 (t, 1H), 8.29 (d, 2H), 8.04 (d, 2H), 4.76 (d, 2H)  
3,5-Dinitobenzohydrazide: m.p.