TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Component: The halo is chloro, bromo, or iodo. The base is a tertiary amine.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Component: The aldehyde or acetal is coupled to the phosphono group(s) by a linking group including aryl, alkyl, alkylaryl, or alkylarylalkyl groups. The halo-substituted porphyrin comprises a porphyrin having a halo group coupled by an intermediate linking group. The porphyrin comprises a component from a double-decker or triple-decker sandwich coordination compound. The trialkylsilylhalide is trimethylsilyl chloride or trimethylsilyl bromide. The base is a trialkylamine. Preferred Method: The method further comprises metalating the porphyrin having a phosphono group. EXAMPLE - A sample of 4-bromobenzaldehyde dimethylacetal was coupled with di-tert-butylphosphite to give 4-(di-tert-butyloxyphosphoryl)benzaldehyde dimethylacetal. The latter was used in a mixed-aldehyde condensation with pyrrole under standard conditions of boron fluoride-diethyl ether(BF3.O(Et)2)-ethanol cocatalysis followed by oxidation with 2,3 dichloro 5,6 dicyano 1,4 benzoquinone (DDQ) to give 5-(4-(Di-tert-butyloxyphosphoryl)phenyl)-10,15,20-trimesitylporphyrin (1). Porphyrin (1) was metalated with zinc acetate dihydrate (Zn(OAc)2.2H2O) in dichloromethane (CHCl3)/methanol to afford zinc (Zn)(II)-5-(4-(Di-tert-butyloxyphosphoryl)phenyl)10,15,20-trimesitylporphyrin (Zn1) in 73% yield. Cleavage of the tert-butyl groups was achieved with trimethylsilyl-chloride (TMS-Cl)/triethanolamine (TEA) in refluxing CHCl3 (stabilized with amylenes) to obtain Zn(II)-5-(4-(dihydroxyphosphoryl)phenyl)- 10,15,20-trimesitylporphyrin (Zn2) without demetalation in 89% yield. The synthesis of magnesium (Mg)(II)-5- (4-(Di-tert-butyloxyphosphoryl)phenyl)10,15,20-trimesitylporphyrin (Mg1) was first tried using the heterogeneous magnesium insertion procedure. Porphyrin (1) was treated with magnesium iodide (MgI2) and diisopropylethylamine (DIEA) in dichloromethane (CH2Cl2) at room temperature. Magnesium insertion using the homogeneous procedure (ethereal MgI2-DIEA reagent in CH2Cl2) gave Mg1 in 71% yield. However, use of TMS-bromide (Br)/TEA in refluxing CHCl3 gave Mg(II)-5- (4-(Dihydroxyphosphoryl)phenyl)-10,15,20-trimesitylporphyrin (Mg2) in 77% yield. The Zn(II)-5-(4-(diethoxyphosphoryl)phenyl)-10,15,20-trimesitylporphyrin (Zn3) which was prepared from 4-(diethoxyphosphoryl) benzaldehyde in the same manner as for zinc iodide (ZnI). We found that Zn3 could be deprotected in 81% yield without affecting the metalation state by using the TMS-Br/TEA reagent in refluxing CHCl3. On the other hand, treatment of Zn3 with TMS-Br in the absence of TEA at room temperature caused demetalation in addition to cleavage of the ethyl groups, affording the free base porphyrin-phosphonic acid 2 in 79% yield. Porphyrin 2 was metalated with Zn(OAc)2.2H2O under standard conditions, giving Zn2 in 77% yield. The successful metalation of a porphyrin bearing a free phosphonic acid was surprising and may stem in part from the suppression of aggregation afforded by the three mesityl groups. The reaction of acetal with excess pyrrole afforded dipyrromethane in 31% yield. Alternatively, palladium-mediated coupling of 5-(4-bromophenyl) dipyrromethane with di-tert-butylphosphite gave dipyrromethane in 43% yield. Dipyrromethane was a valuable synthon for porphyrin chemistry.