Future interests in tangible personal property

For purposes of this section, payment of a charitable contribution which consists of a future interest in tangible personal property shall be treated as made only when all intervening interests in, and rights to the actual possession or enjoyment of, the property have expired or are held by persons other than the taxpayer or those standing in a relationship to the taxpayer described in section 267(b) or 707(b). For purposes of the preceding sentence, a fixture which is intended to be severed from the real property shall be treated as tangible personal property.