DOTP

Developments in the USA have led to the availability of terephthalate plasticisers, for example dioctyl terephthalate (DOTP). Whilst these materials are very similar to the corresponding o-phthalate esters they are generally less volatile and are best compared with d-phthalates with one or more carbon atom in the alkyl chain. As with the linear dialkyl phthalates the terephthalates show good fogging resistance. This is a phenomenon in which new cars on storage fields awaiting delivery develop misting on the windows due, apparently, to the volatility of additives in PVC compounds used with the car. 

Fig. 17. Gd-aqueous proton radial distribution function for the aqueous solution of the Gd(III)(DOTP) complex (after Borel, A. Helm, L. Merbach, A.E. Chemistry - A European Journal 2001, 7, 600-610).

Fig. 18. NMRD profile for Gd(III)(Cn-DOTP) -HSA calculated using the radial distribution function of Fig. 17. Reproduced with permission from Kruk, D. Kowalewski, J. J. Chem. Phys. 2002, 117,1194-1200. Copyright 2002 American Institute of Physics.

Gray LE, Ostby J, Eurr J, Price M, Veeramachaneni DNR, Parks L (2000) Perinatal exposure to the phthalates DEHP, BBP, and DINP, but not DEP, DMP, or DOTP, alters sexual differentiation of the male rat. Toxicol Sci 58 350-365... 

H and 13C NMR studies of the diamagnetic [La(DOTP)]5 and [Lu(DOTP)]5-complexes revealed a high degree of stereochemical rigidity in these compounds [91]. In addition, [Ln(DOTP)]5- complexes possess a remarkable thermodynamic stability with long-lived coordinate bonds rendering them extremely... 

In principle, lanthanide complexes of alkyl- (phosphinates) or alkoxy- (phosphonate esters) DOTP derivatives may give rise to 32 stereoisomers, existing as 16 enantiomeric pairs, which are indistinguishable by NMR spectroscopy. The isomers originate from chiral elements inherent in these complexes, including the R or S configuration at each phosphorus and the helicity defined by the pendant arm orientations (AIA). Various Ln3+ complexes of phosphinate and phosphonate ester ligands derived from 1,4,7,10-tetraazacyclododecane (cyclen) have been described in the literature [104-107]. 

NMRD studies of Gd3+ complexes of DOTPME and DOTPMB indicate q< 1 suggesting that the inner coordination sphere of these complexes is obstructed due to the steric encumbrance of the alkoxy substituents [ 104]. In a multinuclear NMR study of Ln3+ complexes (Ln = La, Gd, Dy, Tm and Yb) with a fluorinated ethyl ester analog of DOTP (F-DOTPME), the 19F NMR spectra reveal up to 16 resonances, which demonstrate that these complexes exist in aqueous solution as a mixture of stereoisomers [105]. [Gd(F-DOTPME)] afforded a water proton relaxivity typical of non-hydrated complexes. 170 NMR of the Dy 1 complex confirmed the lack of a bound water molecule. 

The average lifetime of water molecules in the second coordination shell can be obtained from the MD simulation and was found to be in the range of 20-25 ps for the poly(amino-carboxylate) complexes and 56 ps for the polyamino-phosphonate based [Gd(DOTP)]5- [97]. These residence times are long if compared to those of second sphere water around the aqua ions of lan-... 

Gd-complexes of TETA and DOTP have no inner sphere water molecule and therefore the NMRD profiles reflect directly the second- and outer-sphere relaxivity accessible also from calculations based on the molecular dynamics simulations (Fig. 8). The experimental NMRD profile of [Gd(TETA)]- could be reproduced by drastically changing the electronic relaxation parameters from those... 

Fig. 8. NMRD profile of [Gd(teta)] (top) and [Gd(dotp)]5 (bottom) ,profiles incorporating the electron relaxation parameters determined by Powell et al. for [Gd(dota)(H20] ...

The Gd-DOTP chelate (Fig. 18) has been examined as a potential allosteric effector of hemoglobin [113]. Human hemoglobin is a tetrameric protein whose quaternary structure is affected by an allosteric effector. Binding of this low molecular weight species stabilizes the so-called T-form of hemoglobin, which is characterized by a low oxygen affinity, as opposed to the R-form, a very efficient... 

DOTP ligand are arranged in a propeller-like fashion above the basal plane made up of the four N donor atoms which encompass the R(lll) ion, thereby generating a C4 symmetry axis in these complexes (fig. 40). Four of the residual negative charges are localized on the phos-... 

Also in the mid seventies, a new type plasticizer - dioctyl terephthalate (DOTP) - was introduced by Eastman. DOTP is less volatile and has better low temperature flexibility than DOP, although it is less solvating than DOP or even DIDP. A branched chain Cg terephthalate is reported to be compatible with PVC but not a 70% linear Cg average phthalate. Most C5 and lower tere-phthalates are reported to be incompatible solids(17). 

The use of trimellitates is expected to regain ground lost due to TMA shortages in the late seventies. Polymeries will continue to be used in those areas where high solvent extraction resistance and migration are major concerns. Phosphates are expected to continue their growth in flame retardant applications. Also, new capacity for dioctyl terephthalate (DOTP) has been announced(25). 

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