In my opinion, the "complex" exists in foods to preserve the reduced vitamin C which is otherwise subject to break down.
From the research I have read, if you want to get the most out of the vitamin C you eat, and there isn't enough in foods to be useful (compared to what animals can make for themselves) -- ergo, you must supplement -- you should not eat vitamin C with carbohydrates (as carbs make VC breakdown in the gut). On the other hand, one should eat vitamin C with protein (e.g. amino acids) because the aminos "chelates" the C - protecting it in the gut, and making more VC enter the blood stream intact. (Ref. Sherry Lewin, Vitamin C: Its Biology and Medical Potential, 1976)
Owen R. Fonorow, Follow #OWENRFONOROW at twitter