Inter alia, the first titania-catalyzed [.sup.18F]-radiofluorination in highly aqueous medium is provided. In embodiments, the method utilizes titanium dioxide, 1:1 acetonitrile-thexyl alcohol solvent mixture and tetrabutylammonium bicarbonate as a base. Radiolabeling may be directly performed with aqueous [.sup.18F]fluoride without the need for drying/azeotroping step, which reduces radiosynthesis time while keeping high fluoride conversion. The general applicability of the synthetic strategy to the synthesis of the wide range of PET probes from tosylated precursors is demonstrated.

Inter alia, the first titania-catalyzed [.sup.18F]-radiofluorination in highly aqueous medium is provided. In embodiments, the method utilizes titanium dioxide, 1:1 acetonitrile-thexyl alcohol solvent mixture and tetrabutylammonium bicarbonate as a base. Radiolabeling may be directly performed with aqueous [.sup.18F]fluoride without the need for drying/azeotroping step, which reduces radiosynthesis time while keeping high fluoride conversion. The general applicability of the synthetic strategy to the synthesis of the wide range of PET probes from tosylated precursors is demonstrated.

A crosslinking agent includes a compound represented by the following formula (1).

##STR00001##

wherein R.sup.1, R.sup.2, and R.sup.3 are independently a hydrogen atom, a fluorine atom, an alkyl group, a fluoroalkyl group, or a substituted or unsubstituted aryl group, a plurality of R.sup.1 are identical to or different from each other, a plurality of R.sup.2 are identical to or different from each other, a plurality of R.sup.3 are identical to or different from each other, provided that at least one of R.sup.1, R.sup.2, and R.sup.3 is a hydrogen atom, and at least one of R.sup.1, R.sup.2, and R.sup.3 is a fluorine atom or a fluorine atom-containing group, m is an integer from 2 to 6, l is an integer from 0 to 2, and each hydrogen on the benzene ring(s) may be substituted.

A crosslinking agent includes a compound represented by the following formula (1).

##STR00001##

wherein R.sup.1, R.sup.2, and R.sup.3 are independently a hydrogen atom, a fluorine atom, an alkyl group, a fluoroalkyl group, or a substituted or unsubstituted aryl group, a plurality of R.sup.1 are identical to or different from each other, a plurality of R.sup.2 are identical to or different from each other, a plurality of R.sup.3 are identical to or different from each other, provided that at least one of R.sup.1, R.sup.2, and R.sup.3 is a hydrogen atom, and at least one of R.sup.1, R.sup.2, and R.sup.3 is a fluorine atom or a fluorine atom-containing group, m is an integer from 2 to 6, l is an integer from 0 to 2, and each hydrogen on the benzene ring(s) may be substituted.

A compound having a maximum absorption in a wavelength range of 350 nm to 550 nm that functions as a dichroic dye is provided. In particular, a compound represented by formula (1) is provided. In the compound of formula (1), R.sup.1 represents an alkyl group having 1 to 20 carbon atoms or the like; R.sup.2 represents an acyl group having 1 to 20 carbon atoms or the like; R.sup.3 represents a hydrogen atom or the like; and Y represents a group of formula (Y1). In the formula (Y1), * represents a bonding site with N, or a group of formula (Y2). In the formula (Y2), * represents a bonding site with N; P.sup.1 and P.sup.2 each independently represent —S— or the like; and Q.sup.1 and Q.sup.2 each independently represent ═N— or the like.

##STR00001##

A compound having a maximum absorption in a wavelength range of 350 nm to 550 nm that functions as a dichroic dye is provided. In particular, a compound represented by formula (1) is provided. In the compound of formula (1), R.sup.1 represents an alkyl group having 1 to 20 carbon atoms or the like; R.sup.2 represents an acyl group having 1 to 20 carbon atoms or the like; R.sup.3 represents a hydrogen atom or the like; and Y represents a group of formula (Y1). In the formula (Y1), * represents a bonding site with N, or a group of formula (Y2). In the formula (Y2), * represents a bonding site with N; P.sup.1 and P.sup.2 each independently represent —S— or the like; and Q.sup.1 and Q.sup.2 each independently represent ═N— or the like.

##STR00001##

An object of the present invention is to enable the synthesis of various fluorine-containing compounds having an organic group at both terminals of their tetrafluoroethylene structure (—CF.sub.2—CF.sub.2—). The present invention provides a fluorine-containing complex compound including a fluorine-containing organic metal compound represented by formula (1a):
R.sup.1—CF.sub.2—CF.sub.2-M.sup.1  (1a)
wherein M.sup.1 is a metal selected from the group consisting of copper, zinc, nickel, iron, cobalt, and tin; and R.sup.1 represents an organic group, and at least one ligand selected from the group consisting of pyridine ring-containing compounds and phosphines.

An object of the present invention is to enable the synthesis of various fluorine-containing compounds having an organic group at both terminals of their tetrafluoroethylene structure (—CF.sub.2—CF.sub.2—). The present invention provides a fluorine-containing complex compound including a fluorine-containing organic metal compound represented by formula (1a):
R.sup.1—CF.sub.2—CF.sub.2-M.sup.1  (1a)
wherein M.sup.1 is a metal selected from the group consisting of copper, zinc, nickel, iron, cobalt, and tin; and R.sup.1 represents an organic group, and at least one ligand selected from the group consisting of pyridine ring-containing compounds and phosphines.

The present disclosure provides an organic compound that has a mother skeleton with a fused-ring structure, an electron-withdrawing group bonded to the mother skeleton, and an electron-donating group bonded to the mother skeleton, wherein the electron-withdrawing group is bonded at a position satisfying the following relationship in the mother skeleton.

Σ|C.sub.H|>Σ|C.sub.L|  (1)

(C.sub.H: 2PZ atomic orbital coefficient of a carbon at a substitution site in the HOMO of the mother skeleton)

(C.sub.L: 2PZ atomic orbital coefficient of the carbon at the substitution site in the LUMO of the mother skeleton)

The present disclosure provides an organic compound that has a mother skeleton with a fused-ring structure, an electron-withdrawing group bonded to the mother skeleton, and an electron-donating group bonded to the mother skeleton, wherein the electron-withdrawing group is bonded at a position satisfying the following relationship in the mother skeleton.

Σ|C.sub.H|>Σ|C.sub.L|  (1)

(C.sub.H: 2PZ atomic orbital coefficient of a carbon at a substitution site in the HOMO of the mother skeleton)

(C.sub.L: 2PZ atomic orbital coefficient of the carbon at the substitution site in the LUMO of the mother skeleton)