Is anybody searching for compounds that reduce evil intent? Something that would mellow people out without causing hallucinations. A mass tranquilizer? Not effective against lone operatives but able to be deployed against an invading army.
On a more serious note, anything that's going to affect behavior is going to have a dosage range. Too little absorbed, and there won't be enough effect. Too much, and that will harm / kill people in interesting ways.
With chemical weapons, you only worry about the bio-accumulating enough to kill your enemies. An enemy receiving more than a lethal dose isn't a problem.
> The M44s relatively small production numbers were due, like all U.S. BZ munitions, to a number of shortcomings. The M44 dispensed its agent in a cloud of white, particulate smoke.[3] This was especially problematic because the white smoke was easily visible and BZ exposure was simple to prevent; a few layers of cloth over the mouth and nose are sufficient.[5] There were a number of other factors that made BZ weapons unattractive to military planners.[5] BZ had a delayed and variable rate-of-action, as well as a less than ideal "envelope-of-action".[5] In addition, BZ casualties exhibited bizarre behavior, 50 to 80 percent had to be restrained to prevent self-injury during recovery.[5] Others exhibited distinct symptoms of paranoia and mania.[5]
Of course they are. Among the "evil intent" they would reduce is any desire to rebel against your government, so you bet all big intelligence agencies are looking into it, for instance. Science fiction wrote about this decades ago.
Fortunately, there's a lot of considerations involved in deployment of anything. It's easier said than done to get something of a medical nature into a population surreptitiously, because it's hard to get a certain dose into one person without someone else getting not enough and yet someone else getting way too much. You'd have to come up with a way of delivering a medical dose in a controlled fashion and lie about it or something, you couldn't just sneak it into the food/water reliably.
Further, just because someone can name the exact complicated effect they'd like doesn't mean there's a drug that corresponds to it. Serenity, already mentioned, is a bit of silly example in my opinion because such a large effect should have been found during testing. But it does no good to pacify the population such that they'd never dream of so much as peacefully voting out the current leaders if the end result is that nobody would ever dream of so much as having enough ambition to show up to their jobs and you end up conquered by the next country over without them even trying, simply because they economically run circles around you. Or any number of other possible second-order effects. In a nutshell, it's dangerous to try to undercut evolution just to stay in power if not everywhere decides to do so equally, because you'll be evolved right out along with the society you putative rule. Evolution is alive and well and anyone who thinks it's asleep and they can screw around without consequences is liable to get a lethal wakeup call.
> The report states: “These findings, which are consistent with the finding in clinical trials that lithium reduces suicide and related behaviours in people with a mood disorder, suggest that naturally occurring lithium in drinking water may have the potential to reduce the risk of suicide and may possibly help in mood stabilisation, particularly in populations with relatively high suicide rates and geographical areas with a greater range of lithium concentration in the drinking water.”
