Is it accepted to cite an entire issue of a journal?
It seems tempting to cite only the issue of a journal when it contains several articles that you want to refer to from your introduction. Especially so if it is a special issue directly related to your paper. As to your question whether it is an accepted practice, I haven't seen so, but it could depend on the field of research of course.

Personally, I would advise against using such citations for two main reasons:


You should always try to cite as specific as possible. If you support a stated fact with a citation, the reader should be directed to this fact as directly as possible. In your example of the giant molecules, a reader may be more interested in application A than in giant molecules in general, so it will be helpful if you cite more specifically.
Citations are the basis for many measures of academic impact, and I doubt that citations to journal issues are counted in these measures. The authors of the articles that you intend to cite with a reference to a whole journal issue will certainly not be pleased with this, because you restrain a source of academic reputation for them.