We create these events not to allow the news to go unnoticed
or
We create these events to not allow the news to go unnoticed
It has to be "to not allow". In other circumstances, "not to allow" is possible, however it would have to be part of a contrastive "not to do that ... but rather to do this" construction. As in "We come not to bury Caesar, but to praise him."
If splitting an infinitive makes you nervous, you could paraphrase: "We create these events to prevent the news from going unnoticed."