Chemistry does not regulate antimatter. Matter/antimatter annihilation is a fundamental particle interaction. When particles overlap, annihilation should happen instantly. No crystal structure or molecule can delay it to make a regulated reaction. That's pure Trek fiction, again, not actual physics. Calling this dilithium as in Trek is like saying a goat with one horn is a unicorn.
It actually gets worse than that. If we were to take what's in the TNG tech manual concerning the properties of dilithium seriously, we'd have to swallow this nugget on page 60:
the dilithium crystal... is the only material known to Federation science to be nonreactive with antimatter when subjected to a high-frequency electromagnetic (EM) field in the megawatt range, rendering it "porous" to antihydrogen.
So not only do dilithium crystals have a magic property, but also no other substance known by the 24th century has it. It's either dilithium crystals or nothing. If for some crazy reason, you'd want to bang your head against the wall to somehow make
real dilithium exhibit this magic property, then a condition of that occurring is that every other substance we'd know of if you'd ever pull it off (assuming you did it by the 24th century) must also
lack that property.
Of course, the only reason it's framed this way is not for any scientific reason at all. It's to support the scarcity of the resource in the context of the fictional universe.
This example illustrates one of the big problems with all technobabble, when it's taken literally.
For an assertion to be scientific, it must be testable by experiment. Once the technobabble used to describe magic technology gets too specific, it cannot stand up to real world experiments. How could it? If a writer actually could make it stand up, for example in the case of an FTL device, then they'd literally have invented practical FTL!
What you mention, "No crystal structure or molecule can delay [annihilation] to make a regulated reaction," that's supported by all experiment. The claim on page 60 of the TNG tech manual has no evidential support whatsoever, relative to our science, and the likelihood that it ever could be supported by experiment is nil.
Assigning the crystal name a formula doesn't improve fidelity or realism. In fact it worsens these things, because it creates even more reasons for the substance to fail to live up to experimental demands.
I really don't understand the appeal of this kind of technobabble. Perhaps for some people it helps to suspend disbelief by forestalling contact with reality by some kind of bewilderment or obfuscation?