Programmable Nuclear-Spin Dynamics in Ti(IV) Coordination Complexes

Abstract

Interstitial patterning of nuclear spins is a nascent design principle for controlling electron spin superposition lifetimes in open-shell complexes and solid-state defects. Herein we report the first test of the impact of the patterning principle on ligand-based nuclear spin dynamics. We test how substitutional patterning of ¹H and ^79/81Br nuclear spins on ligands modulates proton nuclear spin dynamics in the ligand shell of metal complexes. To do so, we studied the ¹H nuclear magnetic resonance relaxation times (T₁ and T₂) of a series of eight polybrominated catechol ligands and six complexes formed by coordination of the ligands to a Ti(IV) ion. These studies reveal that ¹H T₁ values can be enhanced in the individual ligands by a factor of 4 (from 10.8(3) to 43(5) s) as a function of substitution pattern, reaching the maximum value for 3,4,6-tribromocatechol. The T₂ for ¹H is also enhanced by a factor of 4, varying by ∼14 s across the series. When complexed, the impact of the patterning design strategy on nuclear spin dynamics is amplified and ¹H T₁ and T₂ values vary by over an order of magnitude. Importantly, the general trends observed in the ligands also match those when complexed. Hence, these results demonstrate a new design principle to control ¹H spin dynamics in metal complexes through pattern-based design strategies in the ligand shell.

Graphical Abstract

INTRODUCTION

Next-generation applications of open shell magnetic complexes rely on long-lived electronic spin superposition lifetimes. Applications for sustained molecule-based spin superpositions span quantum sensing,^1,2 quantum computation,^3,4 and dynamic nuclear polarization.⁵ Toward utility in these applications, chemical design principles for lengthening superposition lifetime are critically important.^6–11 However, the realization of useful lifetimes (>100 μs) in molecules are still only achieved in environments engineered to be free of a spin bath, in terms of both nuclear and electronic spins.^12,13 Special environments like these are disjoint from applications, wherein highly active local spin environments are likely to be present. Hence, testing new design strategies to prolong spin superposition lifetime in dynamic magnetic surroundings is a pressing concern.

One prominent origin of short-lived spin superpositions in open-shell molecules is the dynamic nuclear spin bath.¹⁴ Rapid and numerous fluctuations in the orientations of these nuclear spins, when close to an electronic spin, impose a fluctuating local magnetic field on the electron, which accelerates the collapse of electronic spin superpositions. The extent to which environmental nuclear spins impart this fluctuating local field depends on their respective nuclear relaxation dynamics. In turn, these dynamics stem (in part) from the respective interactions between the nuclear spins.^15–18 Hence, controlling the spin–spin interactions between bath nuclear spins may be a powerful method for manipulating the dynamic field and producing long-lived molecular electronic spin superpositions.

In this context, a set of chemical design principles to tune the magnetic environment imposed by the nuclei in a molecule would be extremely useful. Here, manipulation of the impact of this proximate “edge” of the larger nuclear spin bath could be achieved via synthetic modification of interspin distances, relative arrangements, and identity of nuclear spins on the molecule itself. Indeed, recent breakthroughs from our group on V(IV) complexes¹⁹ and others on the solid-state defects in SiC^20–22 provide preliminary demonstrations of manipulating nuclear spin position/arrangements to control nearby electronic spin superpositions. Extensive literature exists on the fundamental mechanisms governing nuclear spin relaxation, ^15–18 providing a foundational backbone for translating the aforementioned breakthroughs into broadly applicable design principles. Yet, generalizable synthetic strategies to tailor nuclear spin relaxation in the ligand shell of metal complexes are still absent.

Toward that knowledge, we herein test the dependence of ¹H nuclear-spin dynamics on substitutional patterning in a series of brominated catechol derivatives and upon coordination to Ti(IV) (Figure 1). We hypothesized that different patterns of Br functional groups on the ligand would enable a significant synthetic variation in ¹H spin dynamics in the isolated catechols, as bromine and hydrogen have significantly different nuclear magnetic moments (¹H, μ = 2.79 μ_N, ⁷⁹Br, μ = 2.11 μ_N, ⁸¹Br, μ = 2.27 μ_N) and Larmor frequencies (at 9.4 T, ¹H = 400 MHz, ⁷⁹Br = 101 MHz, ⁸¹Br = 108 MHz). We thus reasoned that different substitutional patterns on the ligand shell would modulate the interspin dipole–dipole interactions, thereby impacting T₁ and T₂.²³ The difference in Larmor frequencies was also viewed as particularly advantageous for suppressing the impact of nuclear Overhauser effects on relaxation and simplifying the analysis.²⁴ Finally, we predicted that these trends would be reproduced when the ligands were part of the coordination shell. This last prediction is on the basis of the distance dependence of the dipolar interactions between nuclei, which weaken with r⁻⁶ (where r is the distance separating nuclei).^37–39 Hence, we envisioned that interligand interactions would be minimal relative to intraligand interactions.

Figure 1.

In this manuscript, we perform the first tests of how different substitutional patterns of ¹H and ^79/81Br nuclear spins on ligands impact the ligand ¹H T₁ and T₂ and how the effect changes upon coordination.

To test the foregoing hypotheses, we investigated the ¹H spin–lattice relaxation (T₁) and spin–spin relaxation (T₂) times for eight catechol molecules: pyrocatechol (1), 3-bromocatechol (2), 4-bromocatechol (3), 3,5-dibromocatechol (4), 4,5-dibromocatechol (5), 3,4,5-tribromocatechol (6), 3,4,6-tribromocatechol (7), and tetrabromocatechol (8) (Figure 2). We also selected six specific titanium complexes from this set of ligands for investigation: [Ti(C₆H₄O₂)₃]²⁻ (1a), [Ti(C₆H₃-4-BrO₂)₃]²⁻ (3a), [Ti(C₆H₂-3,5-Br₂O₂)₃]²⁻ (4a), [Ti(C₆H₂-4,5-Br₂O₂)₃]²⁻ (5a), [Ti(C₆H-3,4,5-Br₃O₂)₃]²⁻ (6a), and [Ti(C₆Br₄O₂)₃]²⁻ (8a) (Figure 2), all isolated as the Me₂NH₂⁺ salts. We found that substituting ^79/81Br in a ¹H spin system extends ¹H T₁ and T₂ by a factor of 4, depending on the pattern of the substitution. When complexed with Ti(IV), the ligand protons mimic the relaxation trends of the uncomplexed ligands. Yet, the relative variation is considerably more dramatic in the studied complexes, as ¹H T₁ and T₂ are enhanced by an order of magnitude depending on substitutional pattern. These data provide the first evidence of a synthetic design principle for modifying nuclear spin dynamics via substitutional patterning, and that coordination enhances the relative impact of the pattern design principle.

Figure 2.

Synthetic scheme and complexes. (a) The general synthetic scheme to produce the titanium complexes is depicted. (b) The series of ten ligands used in this study. (c) Ligands 1, 3–6, and 8 were reacted to form six Ti(IV) coordination complexes following the scheme shown in (a).

RESULTS

Isolation of the studied molecules proceeded with little difficulty. Indeed, many of the brominated catechols are available commercially (1, 2, 3, 8) and all others were prepared via slight modifications of reported procedures (4–7).^25–27 Overnight reactions of 3.3 equiv of the catechols 1, 3, 4, 5, 6, and 8 with 1 equiv of Ti(NMe₂)₄ in THF yielded dark red solutions containing 1a, 3a, 4a, 5a, 6a, or 8a (Figure 2), which can be isolated as orange powders. These reactions produce Me₂NH₂⁺ counterions, suggesting that the Me₂N⁻ ligands of the Ti(IV) starting material Ti(NMe₂)₄ are deprotonating the catechol ligands during reaction progression. This same counterion formation by ligand deprotonation characterizes the synthesis of the analogous V(IV) complexes.^28,29

Single-crystal X-ray diffraction of crystals resulting from the reactions of 1 and 5 with Ti(NMe₂)₄ reveals an octahedral geometry for the TiO₆ coordination environment (Figures 3 and S1, Tables S1–S3). These experiments reveal a general 3-to-1 ligand-to-metal stoichiometry and two Me₂NH₂⁺ counterions. All other characterization data for the metal complexes match this general stoichiometry, though isolating high-quality single crystals of 3a, 4a, 6a, and 8a was significantly more challenging (see SI). Bond metrics taken from the obtained structures match literature expectations. For example, the average Ti–O distances in 1a and 5a are 1.9640(3) and 1.993(5) Å, respectively, close to those of known Ti-catecholate analogues.^30–32 Furthermore, C–O bond distances in the ligands are 1.345(8) Å which match those for the fully reduced catecholate, suggesting closed-shell ligands (as opposed to possible semiquinones, where C–O is 1.302(11) Å).³³ These data establish these molecules as closed-shell Ti(IV) complexes.

Figure 3.

Molecular structures of [Ti(C₆H₄O₂)₃]²⁻ (left) and [Ti(C₆H₂Br₂O₂)₃]²⁻ (right), as determined in the crystal structures of 1a and 5a. Hydrogen bonding contacts with the Me₂NH₂⁺ counterions are omitted for clarity. Orange, maroon, red, gray, and white spheres represent titanium, bromine, oxygen, carbon, and hydrogen atoms, respectively.

Proton NMR spectroscopy (400 MHz, 9.4 T) was applied to the ligands and complexes to locate and identify the chemical shifts of the nuclei of interest. All ligands and complexes depict ¹H peaks in the aromatic region (save for 8 and 8a, which have only aromatic ^79/81Br nuclear spins). Here, the peaks appear to be shifted downfield by proximity to either hydroxy or bromine groups. Furthermore, these peaks are split by J-coupling, where J is largest for 1,2-coupling between ortho protons (5.86–8.43 Hz) and decreasing as the protons are spaced apart on the catechol ring (2.05–3.57 Hz for 1,3-coupling between meta ¹Hs).³⁴ The 1,4-coupling strength between para ¹Hs was too small to observe for 1, 3, and 5 in our spectrometer. Peaks corresponding to OH groups for the free ligand show up from 7.76 to 9.22 ppm. The Me₂NH₂⁺ counterions show peaks at 2.60 and 8.09–8.60 ppm for the −CH₃ and NH₂ protons, respectively, in the complexes. Upon complexation to Ti(IV), the catecholate ¹H aromatic peaks move slightly upfield but otherwise retain the same relative δ values and J couplings. The exception to the spectral similarity is complex 3a, which exhibits rearranged peaks due to the removal of the shifting effect from the hydroxyl protons (Figures S3 and S9 in the SI).

Spin–lattice relaxation times were determined by standard ¹H NMR inversion–recovery experiments at room temperature (see Figures 4 and S2–S7 and the SI) for all ligands and complexes. These experiments proceeded with π pulses of 22 μs, and all catechol solutions were 200 mM in acetone-d₆. All Ti(IV) complexes were measured at 100 mM in DMSO-d₆ (solubility challenges precluded the use of acetone—see SI). NMR spectra were then collected following the initial π pulse, a variable-delay period, T, and a final π/2 pulse. For all ligands and complexes, the initial spectra following the π pulses are inverted, eventually recovering to the expected positive signal intensity. All recoveries were successfully fit with mono-exponential functions, suggesting that only a single relaxation process dominates for each peak. Importantly, the time scale of this recovery is peak-dependent (Figures 4 and S2–S8).

Figure 4.

Example ¹H NMR analyses of a catechol molecule, here 1. (a) Inversion–recovery spectra—the offset spectra represent different delay times between inversion and measurement, with the shortest delays at the bottom in green. (b) Depiction of ¹H peak assignment. (c) Peak intensity as a function of delay following inversion. The black line is a fit to an exponential recovery to yield T₁ for a given peak. (d) CPMG experimental results—the offset spectra represent different numbers of applied π pulses: the green spectrum at the bottom was collected with one π pulse and the red spectrum at the top was collected with 12 π pulses. (e) ¹H peak intensity versus total time after the π/2 pulse. The black line is a fit to an exponential decay to yield T₂ for the indicated peak.

Our results show that, with minor exceptions, the substitution of Br atoms for H atoms engenders longer ¹H T₁ times (Table 1), based on four key observations. First, the shortest T₁ values are observed for protons that are adjacent to other protons. For example, the adjacent protons of 2 have T₁ times of 10.8(4) and 11.9(2) s, respectively, the shortest of 1–8. This general trend holds true for the adjacent protons in 1 and 3, which exhibit aromatic ¹H T₁ values only slightly longer compared to 2, ca. 13–14 s. Second, the presence of a Br atom adjacent to a ¹H (versus another proton) appears to have a slight lengthening effect on T₁. Indeed, in 2, the proton in the 4-position (which has one adjacent proton and one adjacent bromine) exhibits a slightly longer T₁ (17.9(4) s) than the other two protons of this ligand, which lack a neighboring Br atom (10–12 s). Third, T₁ is further lengthened when the Br atom isolates a given proton from other protons. For example, the ¹H in the 3-position of 3, which is separated from the other protons, exhibits a relaxation time of 27(3) s, nearly twice as long as the proton in the corresponding position on 1. Similarly, for 4 and 5, which have no adjacent protons, the ¹H T₁ values are extended to 28–31 s. Finally, fourth, when only one aromatic ¹H is present (as in the triply brominated 6 and 7), T₁ can become even longer (32(4) and 43(5) s). In summary, these data demonstrate that T₁ can be varied by a factor of approximately four depending on the substitutional pattern.

Table 1.

Tabulated Aromatic ¹H Spin–Lattice Relaxation Times (T₁) Determined via Inversion Recovery Experiments^a,b,c

	Ring Position
Ligands	3	4	5	6
1	14.8(7)	13.3(6)	13.3(6)	14.8(7)
2		17.9(4)	10.8(4)	11.9(2)
3	27(3)		13.7(6)	13.4(7)
4		30(5)		31(5)
5	28(4)			28(4)
6				32(4)
7			43(5)
	Ring Position
Complexes	3	4	5	6
1a	1.32(2)	2.11(6)	2.11(6)	1.32(2)
3a	0.48(2)		0.74(8)	0.38(3)
4a		6.3(5)		6.8(3)
5a	6.0(5)			6.0(5)
6a				7.1(2)

^aAll T₁ values given in units of s.

^bThere are no aromatic protons for 8 and 8a, hence the omission.

^cT₁ values for OH groups and Me₂NH₂⁺ counterions can be found in the SI.

The aromatic ¹H signals for the ligands display shorter overall T₁ values when coordinated to Ti(IV) (Figures 5, S9–S13, and Table 1). However, (and importantly), the same trends in ¹H T₁ values as a function of Br substitution patterns are seen for both the complexes and the lone ligands. For example, the adjacent protons in 3a display the shortest T₁ values among the studied complexes, 0.48(2) and 0.38(3) s. In contrast, 4a–6a, which have ¹H nuclear spins isolated from one another by Br atoms, exhibit T₁ values that are an order of magnitude greater (6.0(5) to 7.1(2) s).

Figure 5.

Example ¹H NMR analyses of a Ti(IV) catecholate complex molecule, here 1a. (a) Inversion–recovery spectra—the offset spectra represent different delay times between inversion and measurement, with the shortest delays at the bottom in green. (b) Depiction of ¹H peak assignment. (c) Peak intensity as a function of delay following inversion. The black line is a fit to an exponential recovery to yield T₁ for a given peak. (d) CPMG experimental results—the offset spectra represent different numbers of applied π pulses: the red spectrum at the bottom was collected with one π pulse, and the fluorescent green spectrum at the top was collected with 10 π pulses. (e) ¹H peak intensity versus total time after the π/2 pulse. The black line is a fit to an exponential decay to yield T₂ for the indicated peak.

Tests of the effects of substitutional pattering on ¹H T₂ were performed through application of Carr–Purcell–Meiboom–Gill (CPMG) experiments (Figures 4, 5, S2–S7, and S9–S12).^35,36 This experiment is similar to a Hahn-echo experiment; however, the time separating sequential π pulses is fixed, and the number of π pulses is varied, such that the total delay time between the initial pulse and the observed echo is the sum of repeated pulses and fixed delays. Application of the CPMG sequence to obtain T₂ removes field inhomogeneities as a potential impact on spin–spin relaxation—ensuring any determined trends are attributable to the studied complexes and not extrinsic effects. As with T₁, the time-dependent data set could be effectively modeled with a single exponential function, implying a single relaxation process is dominant. Critically, as with T₁, T₂ is peak-dependent.

The T₂ times of the aromatic protons in 1–8 broadly follow the trends seen in the T₁ data—greater degrees of bromination produce longer ¹H T₂ values (see Table 2). For example, the adjacent ligand ¹Hs on 1 were found to have T₂ parameters of approximately 5 s, which are the shortest of the series (second to 6, see below). The singly brominated ligands 2 and 3 both have T₂ values that are larger than 1, again consistent with T₁ trends. Furthermore, protons in 3 and 5 that are isolated from the others by bromination show similar T₂ values. The doubly brominated 5’s T₂ values fall within the range of 3’s relaxation times. In contrast, the compositional isomer to 5, with relatively closer ¹H spins, 4, shows >60% relative lengthening of T₂. The two triply brominated ligands also display radically different T₂ values. 6 was found to have a T₂ of 4.30(4) s, shorter even than 1. In contrast, 7 exhibits the longest T₂ of all of the ligands, 18(1) s, exceeding the T₁ of pyrocatechol. In summary, these data show substantial variation in T₂ with substitutional patterning that mimics the trends in T₁.

Table 2.

Tabulated Aromatic ¹H Spin–Spin Relaxation Times (T₂) Determined with CPMG Pulse Sequences^a,b,c

	Ring Position
Ligands	3	4	5	6
1	5.1(2)	5.0(2)	5.0(2)	5.1(2)
2		6.3(6)	5.4(6)	6.0(3)
3	6.8(2)		6.5(2)	6.3(2)
4		10.9(9)		9.8(6)
5	6.5(3)			6.5(3)
6				4.30(4)
7			18(1)
	Ring Position
Complexes	3	4	5	6
1a	0.85(7)	0.9(3)	0.9(3)	0.85(7)
3a	0.22(1)		0.22(2)	0.23(1)
4a		3.42(4)		2.87(1)
5a	2.65(4)			2.65(4)
6a				2.88(5)

^aT₂ values given in units of seconds.

^bThere are no aromatic protons for 8 and 8a, hence the omission.

^cT₂ values for OH groups and Me₂NH₂⁺ counterions can be found in the SI.

As with T₁, the spin–spin relaxation times of the aromatic ¹H ligand peaks all decrease upon complexation and generally follow the trends in T₁. For example, the ligand ¹Hs in 1a exhibit the second-shortest T₂ values (∼0.9 s), generally smaller than complexes where ¹H spins are separated by bromines, which have T₂ parameters ranging from 2.65(4) s in 5a to 3.42(4) s in 4a. But, there are a few important exceptions in the correlation to T₁. For example, the aromatic ¹H peaks of 3a have the shortest T₂ values of the studied complexes (0.22(1) to 0.23(1)) s, despite having a Br atom. Second, the complex with triply brominated ligands, 6a, has a T₂ that is within the range of the other complexes (2.88(5) s), when the ligand for this complex, 6, has the longest T₂ of all the ligands. These few exceptions point to more complicated relaxation dynamics in the complexes than dipole effects from only the ligand shell, in contrast to the pure ligands.

DISCUSSION

The collected NMR data paint a rich picture of the ¹H nuclear spin dynamics within the studied species and reveal a path toward bespoke nuclear magnetization dynamics in the ligand shell. The results further point toward dipole-driven relaxation processes as the synthetically tunable feature. Here, whenever a proton is replaced by a ^79/81Br nucleus in a given ligand, the strong ¹H···¹H interaction of that proton with neighboring ones is replaced by the relatively weaker coupling to the bromine (as ^79/81Br have a smaller magnetic moment). This switch results in the general lengthening of both T₁ and T₂ for the ¹H spins with increasing bromine content across the series of tested ligands. In the following analyses, note that we ignore the impact of potential ¹³C nuclear spins in the ligands, as this I = ¹/₂ isotope is only 1% naturally abundant.²³

We tested the correlation between ¹H relaxation times and dipolar interactions to better quantitate the T₁/T₂ trends for the studied species. For this test, we computed the ¹H dipole-driven spin–lattice (T₁^DD) and spin–spin (T₂^DD) relaxation times which stem from a sum of dipole–dipole interactions with all surrounding magnetic nuclei and a rotational correlation time (Figure 6), τ_c^37–39 (see SI for detailed equations and interpretation). Comparison of the experimental T₁ and T₂ values with the computed values is shown in Figures 6 and S14. Relatively good linear correlations are seen for T₁ (R² = 0.91), when the τ_c values for all protonated catechol ligands (1–7) are assumed to be 9 ps, as is typical of small molecules.³⁶ Low correlation with T₂ is observed, however, which may stem from the CPMG sequence, as well as the fundamental assumption of the same τ_c for all ligands (see SI). When the experimental T₁ is set as T₁^DD, numerical solutions for τ_c are obtained. The determined τ_c values via this method range from ca. 6 to 12 ps, well within the bounds of what is reasonable for small organic molecules (Table S5).^40–42 This slight variation in τ_c for protons in ligands/complexes with nearly the same chemical composition likely stems from differences in mass distributions (owing to the heavy Br atoms), which will affect motion in solution.^43,44

Figure 6.

(a) Each proton in the ligand experiences dipolar interactions with other nuclear spins in its vicinity. Rotation of the molecule (on a time scale called the correlation time, τ_c) impacts the T₁ and T₂ of a spin of interest through dipolar coupling between the spin of interest and other nuclear spins in the environment. (b) Comparison of the experimental ¹H ligand T₁ relaxation times with the computed T₁ considering only dipole–dipole interactions, T₁^DD and assuming the same τ_c, 9 ps, for 1–7 (8 has no protons on the ligand shell). The high correlation between the two data sets (gray line, R² = 0.91) suggests that spin–lattice relaxation in these systems is governed predominantly by dipole–dipole effects between a given proton and its nearest neighbors.

Similar comparison of experimental ¹H T₁/T₂ with T₁^DD/T₂^DD for the metal complexes is of lower quality, and τ_c cannot be extracted in some cases, unlike the ligands (Table S5). When τ_c times can be extracted, they are categorically longer than those for the ligands, consistent with the picture of decreased relaxation times for longer τ_c values in small molecules. Furthermore, the general trend in spin dynamics from the ligands carries over to the metal complexes: when protons are separated by Br atoms, ¹H spin relaxation becomes slower. On this basis, we conclude that the general mechanism of ¹H spin relaxation in the ligands is likely also present in the metal complexes. Precise modeling of T₁ and T₂ here would require accounting for intramolecular association (as is known for catechol),⁴⁵ and ligand-to-ligand and ligand-to-H₂NMe₂⁺ interactions. We posit that the impact of the counterion is relatively weak. Otherwise, T₁ and T₂ would be smaller for every ¹H in the 3 and 6 positions of the studied complexes, as these positions are closest to the hydrogen-bonded counterion. In this light, 3a and 4a are important, as the 3- and 6-position protons here have T₁ or T₂ values that are comparable or longer than protons in the 4 and 5 positions. Other factors that prevent perfect correlation include lengthening of T₂ via the quantum zeno effect⁴⁶ and other relaxation processes, e.g. scalar or chemical shift anisotropy processes, though they are relatively minor contributions to ¹H T₁ and T₂ compared to the dipolar mechanism.^36,37 Future studies by us will test many of the foregoing ideas, especially counterion effects.

As one final point, the impact of the bromination in the ligands and complexes could be linked to manipulation of τ_c, not control of dipolar interactions. However, the trends in τ_c do not follow the trends in T₁ or T₂. For example, the longest T₁ observed in the ligands is 43(5) s for 7, yet this ligand exhibits a correlation time (τ_c = 8.8 ps) within the range of all of the other ligands (6.1 to 12 ps). Furthermore, the shortest τ_c times for the metal complexes were found for 1a, yet this complex does not display the shortest T₁ and T₂ for the studied complexes. We take this observation and the correspondence of the trends in the ligands and complexes as the final evidence that the operative mechanism by which spin patterning affects relaxation is through dipolar interactions.

It is noteworthy that comparison of the foregoing results with trends in ¹H T₁ and T₂ for other ligand systems is nearly impossible, since explicit studies targeting ligand nuclear spin dynamics via synthetic design are, to the best of our knowledge, unrepresented in the literature. We can, however, compare our results with studies of proton spin dynamics in simple haloalkanes. Here, our results agree with these previous studies, which found increasing T₁ and T₂ with increasing degree of halogenation via weakening the overall ¹H···¹H dipolar interactions.^38,39 These studies found relative variation in T₁ of up to a factor of 16, slightly lower than we found for our metal complexes, but beyond what we observed for the isolated ligands. This benchmark underscores the high tunability in the nuclear spin-dynamics of ligands (given the discovery of the right design strategies) and also the importance of coordination.

OUTLOOK

The dynamics of nuclear spins close to metal-based electronic spins are profoundly important for determining electronic spin relaxation times. Yet, understanding how to control those nuclear spin dynamics to precisely direct the magnetic properties of metal ions is a significant fundamental challenge. This paper represents an important step toward that goal by clearly demonstrating (1) the possibility of controlling the dynamics of ligand-based nuclei via patterning and (2) that design principles for isolated ligands can be translated directly to metal complexes (if that metal is closed-shell). Importantly these results also demonstrate that the design principles for T₁ and T₂ are enhanced upon coordination, suggesting that future studies of nuclear spin dynamics in the ligand shell will yield significant fundamental insight. An enormous body of knowledge targets understanding how coordination geometry, symmetry, donor atom strength, etc. affect electron spin relaxation in metal complexes (e.g., refs 47–53). But, to the best of our knowledge, none has tested direct synthetic manipulation of the nuclear spin dynamics within the ligand shell as a potential design parameter for lengthening electron spin relaxation. We thus hope that this work and others from our group will inspire future studies in this undoubtedly rich area.