You'll have to make sure that both APs support 802.11a. 802.11n is a technology supported on both WiFi frequency bands, so it does not indicate which band you are on.
If AP1 supports only .11a and AP2 only .11b/g/n, it will not work, as both APs will be on different frequency bands. For example, your first research probably lead you to "b to gn" and "ac to an".
Consumer-side, the 2.4GHz is represented by 802.11b/g/n, and the 5GHz by 802.11a/n/ac. There is other WiFi standards but it is not relevant to the answer.