MDMA, LSD, Shrooms, etc. These drugs are incredibly powerful and can make a human feel an intense feeling of love and compassion. A sense of unity with the universe.
As for a drug that can make you artificially love a specific person or last for a life time, there isn’t anything that can replicate that as far as I know.
Love is not a feeling which can be induced by chemicals. Love is a set of actions through which you become a better person. This complex process can not be created in a lab.
Love is just chemical reactions. That doesn't mean its simple. I wouldn't be suprised if you could create a drug that stimulates your brain in a similar way to being in love, but I don't see how your could tie it to a specific person. Love is not as simple as some chemicals sitting in your brain making you feel good. Its involved in how you think about a person, how you value their own needs, care about their emotional state. Sitting around staring into someone's eyes and sighing isn't love, its teenage infatuation. Love isn't just a transitory emotion, its a way of thinking about someone.