commit suicide OR suicide

Suicide is a noun, not a verb.

She tried to commit suicide. (~ correct)
She tried to suicide. (~ wrong)

Be very careful, only a few verbs are used with the noun “suicide”.
commit suicide, attempt suicide, contemplate suicide

Some adjectives that go with suicide:-
political suicide, economic suicide

2011-04-03 00:33:52 補充：
Thank 回答者F.P: for correcting me.
Suicide can be used as a verb in America as I have just found out from Webster and Yahoo dictionary, but it is not listed as a noun in most British dictionaries (Oxford, Cambridge, Collins, Longman and Penguin) and Google dictionary.

Suicide 可以解:
自毀事業,前途的行為

2011-04-03 00:56:09 補充：
Sorry, typo error:
... but it is not listed as a verb in most British dictionaries ~ correction
(not "noun",replace it with "verb")

Suicide can be a verb - please see below:

http://www.infowars.com/articles/life/indian_woman_suicides_donate_corneas_blind_son.htm

(i) He commits suicide
(ii) He suicides

Both are correct.