Go here to start:
http://www.irs.gov/publications/p557/ch03.html#d0e3260.
Contributions to 501(c)(3) Organizations
Contributions to domestic organizations described in this chapter, except organizations testing for public safety, are deductible as charitable contributions on the donor's federal income tax return.
Fund-raising events. If the donor receives something of value in return for the contribution, a common occurrence with fund-raising efforts, part or all of the contribution may not be deductible. This may apply to fund-raising activities such as charity balls, bazaars, banquets, auctions, concerts, athletic events, and solicitations for membership or contributions when merchandise or benefits are given in return for payment of a specified minimum contribution. If the donor receives or expects to receive goods or services in return for a contribution to your organization, the donor cannot deduct any part of the contribution unless the donor intends to, and does, make a payment greater than the fair market value of the goods or services. If a deduction is allowed, the donor can deduct only the part of the contribution, if any, that is more than the fair market value of the goods or services received. You should determine in advance the fair market value of any goods or services to be given to contributors and tell them, when you publicize the fund-raising event or solicit their contributions, how much is deductible and how much is for the goods or services. See
Disclosure of Quid Pro Quo Contributions in chapter 2.
I'm not aware of any clause allowing temporary 501c3 status to hold a benefit for an existing 501c3 entity. I'm also not sure whether a separate entity can utilize the tax exempt status for a benefit. There are instances where a "taxable" entity can purchase items tax-free for incorporation to a product or service provided to the 501c3 though.