Non-radiative deactivation of the excited states of europium, terbium and ytterbium complexes by proximate energy-matched OH, NH and CH oscillators: an improved luminescence method for establishing solution hydration states

Beeby, Andrew; Clarkson, Ian M.; Dickins, Rachel S.; Faulkner, Stephen; Parker, David; Royle, Louise; Sousa, Alvaro S. de; Williams, J. A. Gareth; Woods, Mark

doi:10.1039/a808692c

Cited by 1,418 publications

(1,640 citation statements)

References 40 publications

(61 reference statements)

Supporting

Mentioning

1,524

Contrasting

Unclassified

Order By: Relevance

“…To directly assess the influence of the TACN scaffold on the number of bound water molecules, the Eu(III) complex of TACN-1,2-HOPO was prepared for luminescence 13 yielded a q value of 2.9 ± 0.5 at pH 7.0, in excellent agreement with the molecular modeling results and verifying a 9-coordinate metal geometry for TACN-capped hexadentate HOPO ligands.…”

Section: Nih Public Accesssupporting

confidence: 67%

“…TACN-1,2-HOPO is synthesized in a similar manner, replacing 5 with thiazolide-activated 1,2-HOPO (Scheme S2). The effect of the TACN cap on aqueous solubility is dramatic, as more than a 1000-fold increase in solubility over that observed for the parent Gd-TREN-tris-3,2-HOPO complex (1) was determined for 3 (~100 mM).To directly assess the influence of the TACN scaffold on the number of bound water molecules, the Eu(III) complex of TACN-1,2-HOPO was prepared for luminescence 13 yielded a q value of 2.9 ± 0.5 at pH 7.0, in excellent agreement with the molecular modeling results and verifying a 9-coordinate metal geometry for TACN-capped hexadentate HOPO ligands.Relaxivity measurements were obtained for 3 and 4 to determine if the complexes deliver the predicted relaxation enhancements. Relaxivities of 13.1 and 12.5 mM -1 s -1 (20 MHz, 298 K, pH 7) were obtained for 3 and 4, respectively, and are among the highest known values of low-molecular weight mononuclear Gd complexes.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Highly Soluble Tris-hydroxypyridonate Gd(III) Complexes with Increased Hydration Number, Fast Water Exchange, Slow Electronic Relaxation, and High Relaxivity

et al. 2007

View full text Add to dashboard Cite

The design, synthesis, and relaxivity properties of highly soluble TACN-capped trishydroxypyridonate Gd(III) complexes are presented. Molecular mechanics modeling was used to help design a complex capable of possessing three water molecules in the inner metal coordination sphere, an attractive property for high-relaxivity MRI contrast agents. The measured relaxivities of 13.1 and 12.5 mM -1 s -1 (20 MHz, 298 K) for two TACN-capped complexes are among the highest known relaxivities of low-molecular weight Gd complexes and are consistent with three coordinated waters, an extremely fast water exchange rate and long electronic relaxation time. Luminescence measurements to confirm the number of coordinated water molecules for the first time in the HOPO series are also discussed.Magnetic Resonance Imaging (MRI) is a powerful diagnostic technique in modern medicine, and the emergence of new instrumentation and applications invites the production of contrast agents with enhanced imaging capabilities. Contrast agents are evaluated on the basis of their proton relaxivities (r 1p ), and current values for commercial agents (based on poly-(aminocarboxylate) ligands) are small (r 1p = 4 -5 mM -1 s -1 ; 20 MHz and 298 K) compared to what is theoretically possible. 2,3 To obtain the high relaxivities predicted by theory, there are several parameters that must be optimized, including: q, the number of bound waters, τ m , the mean water residence time, τ s , the metal electronic relaxation time, Correspondence to: Kenneth N. Raymond.raymond@socrates.berkeley.edu . Supporting Information Available: Detailed synthesis and characterization of 3 and of TACN-1,2-HOPO, temperature dependence of the paramagnetic contribution to the water 17 O NMR transverse relaxation rate (R 2p ) for 3, and details of the luminescence and stability measurements. This information is available free of charge via the internet at http://pubs.acs.org. Here we report stable, soluble complexes with optimal hydration, water exchange, and electronic relaxation properties, representing major advances toward that goal. NIH Public AccessIn 1995, a Gd complex was described that showed promise as a contrast agent, Gd(TREN-1-Me-3,2-HOPO)(H 2 O) 2 (1, Figure 1). 6 The r 1p value of this hexadentate hydroxypyridinone-(HOPO) based complex was measured as twice that of commercial agents due largely to the complex's increased number of bound water molecules (q of 2 as compared to 1 for commercial agents). Importantly, the stability of this complex (a critical factor for in vivo use 7 ) is higher than that of clinical agents despite the lower ligand denticity and increase in q. Since this initial report, a series of complexes, all based on the tripodal TREN (tris-(2-aminoethyl)-amine) scaffold, has been prepared in an attempt to optimize the proton relaxation parameters and increase aqueous solubility. 8 Those complexes that show the most promising relaxometric and solubility properties rely on the TREN-capped heteropodal bis-HOPO-TAM design (2, Figure 1). For exa...

show abstract

Section: Nih Public Accesssupporting

confidence: 67%

mentioning

confidence: 99%

Highly Soluble Tris-hydroxypyridonate Gd(III) Complexes with Increased Hydration Number, Fast Water Exchange, Slow Electronic Relaxation, and High Relaxivity

et al. 2007

View full text Add to dashboard Cite

show abstract

“…This shortened lifetime is not due to solvent quenching, since the number of bound water molecules (q) estimated from the lifetime data in H 2 O and D 2 O for this complex is 0.2. 44 Indeed, for these five complexes, the near-zero q values indicate that the 5LI-IAM scaffold effectively protects the Tb(III) ion from direct coordination of solvent. For Tb-SO 3 -, the relatively short lifetime is likely due to a difference in the Tb(III) coordination environment for this complex, in comparison to the others, as indicated by the change in the relative intensities of the 5 D 4  7 F J peaks.…”

Section: Resultsmentioning

confidence: 93%

Predicting Efficient Antenna Ligands for Tb(III) Emission

Samuel

Raymond

2008

Inorg. Chem.

View full text Add to dashboard Cite

ABSTRACT:A series of highly luminescent Tb(III) complexes of para-substituted 2-hydroxyisophthalamide ligands (5LI-IAM-X) has been prepared (X = H, CH 3 , (C=O)NHCH 3 , SO 3 -, NO 2 , OCH 3 , F, Cl, Br) to probe the effect of substituting the isophthalamide ring on ligand and Tb(III) emission in order to establish a method for predicting the effects of chromophore modification on Tb(III) luminescence. The energies of the ligand singlet and triplet excited states are found to increase linearly with the -withdrawing ability of the substituent. The experimental results are supported by 2 time-dependent density functional theory (TD-DFT) calculations performed on model systems, which predict ligand singlet and triplet energies within ~5% of the experimental values. The quantum yield () values of the Tb(III) complex increases with the triplet energy of the ligand, which is in part due to the decreased non-radiative deactivation caused by thermal repopulation of the triplet. Together, the experimental and theoretical results serve as a predictive tool that can be used to guide the synthesis of ligands used to sensitize lanthanide luminescence.

show abstract

“…6 This effect is particularly dramatic for NIR emitting Ln 3+ because of relatively small energy gaps between ground and excited electronic states. 6 12 These materials protect lanthanide cations from sources of nonradiative deactivation; however, they have either limited (e.g., LnVO 4 ) or no absorbance in the UV range. Thus, these inorganic materials are not able to sensitize lanthanide luminescence with the efficiency of organic sensitizers.…”

mentioning

confidence: 99%

A Strategy to Protect and Sensitize Near-Infrared Luminescent Nd³⁺ and Yb³⁺: Organic Tropolonate Ligands for the Sensitization of Ln³⁺-Doped NaYF₄ Nanocrystals

et al. 2007

View full text Add to dashboard Cite

A strategy to sensitize and protect near-infrared (NIR) emitting Nd 3+ and Yb 3+ is presented. Combining protection provided by the inorganic matrix of NaYF 4 nanocrystals and sensitization from tropolonate ligands capped on their surface, the lanthanide cation centered luminescence was observed through the ligand excitation. The extended lanthanide luminescence lifetimes indicate the success of this strategy.Lanthanide-based near-infrared (NIR) emitters have a great potential to serve as bioanalytical reporters for several reasons: (i) NIR photons scatter less than visible photons, improving image resolution. 1 (ii) Biological systems have low native autofluorescence in the NIR energy domain, 2 resulting in higher detection sensitivity due to improved signal-to-noise ratio. (iii) Most luminescent lanthanide complexes are not susceptible to photodecomposition, allowing long or repeated experiments and simplifying sample storage and preparation procedures. Since f−f transitions are Laporte forbidden, 3 free Ln 3+ have low extinction coefficients resulting in low luminescence intensity. Therefore, it is necessary to sensitize these cations through a suitable chromophore ("antenna effect"), 4 an area of research that has been highly active in recent years. 5 However, this approach has intrinsic limitations because lanthanide luminescence is easily quenched through nonradiative routes when the cations are in close proximity to the vibrational overtones of -OH, -NH, and -CH groups present in the sensitizing ligand and/or solvent. 6 This effect is particularly dramatic for NIR emitting Ln 3+ because of relatively small energy gaps between ground and excited electronic states. 6 12 These materials protect lanthanide cations from sources of nonradiative deactivation; however, they have either limited (e.g., LnVO 4 ) or no absorbance in the UV range. Thus, these inorganic materials are not able to sensitize lanthanide luminescence with the efficiency of organic sensitizers.Here we introduce a strategy to overcome the limited lanthanide sensitization by binding organic tropolonate chromophoric groups to the surface of NaYF 4 nanocrystals (NCs), doped with NIR emitting Nd 3+ or Yb 3+ (Scheme 1). Tropolonate (Trop -) was chosen as a capping ligand since it has been previously demonstrated to be a suitable sensitizer for several lanthanide cations emitting in the NIR range when coordinated in KLn(Trop) 4 complexes. 13 These novel systems use the NaYF 4 matrix to protect Ln 3+ from nonradiative deactivations, while a chromophoric coating sensitizes their luminescence.A synthetic method to prepare Nd 3+ or Yb 3+ doped NaYF 4 NCs was developed on the basis of a recently reported synthesis of NaYF 4 NCs (see Supporting Information). 14 The Trop -capped NCs were synthesized using the following procedure. Tropolone was dissolved in methanol, then deprotonated with an equimolar amount of KOH in methanol. Chloroform was added to obtain a 1/1 (v/v) MeOH/CHCl 3 solvent mixture. This solution was added to a purified solution...

show abstract

Non-radiative deactivation of the excited states of europium, terbium and ytterbium complexes by proximate energy-matched OH, NH and CH oscillators: an improved luminescence method for establishing solution hydration states

Cited by 1,418 publications

References 40 publications

Highly Soluble Tris-hydroxypyridonate Gd(III) Complexes with Increased Hydration Number, Fast Water Exchange, Slow Electronic Relaxation, and High Relaxivity

Highly Soluble Tris-hydroxypyridonate Gd(III) Complexes with Increased Hydration Number, Fast Water Exchange, Slow Electronic Relaxation, and High Relaxivity

Predicting Efficient Antenna Ligands for Tb(III) Emission

A Strategy to Protect and Sensitize Near-Infrared Luminescent Nd³⁺ and Yb³⁺: Organic Tropolonate Ligands for the Sensitization of Ln³⁺-Doped NaYF₄ Nanocrystals

Contact Info

Product

Resources

About

Non-radiative deactivation of the excited states of europium, terbium and ytterbium complexes by proximate energy-matched OH, NH and CH oscillators: an improved luminescence method for establishing solution hydration states

Cited by 1,418 publications

References 40 publications

Highly Soluble Tris-hydroxypyridonate Gd(III) Complexes with Increased Hydration Number, Fast Water Exchange, Slow Electronic Relaxation, and High Relaxivity

Highly Soluble Tris-hydroxypyridonate Gd(III) Complexes with Increased Hydration Number, Fast Water Exchange, Slow Electronic Relaxation, and High Relaxivity

Predicting Efficient Antenna Ligands for Tb(III) Emission

A Strategy to Protect and Sensitize Near-Infrared Luminescent Nd3+ and Yb3+: Organic Tropolonate Ligands for the Sensitization of Ln3+-Doped NaYF4 Nanocrystals

Contact Info

Product

Resources

About

A Strategy to Protect and Sensitize Near-Infrared Luminescent Nd³⁺ and Yb³⁺: Organic Tropolonate Ligands for the Sensitization of Ln³⁺-Doped NaYF₄ Nanocrystals