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Amidst population growth and challenges with existing fertilizers, the development of smart and environmentally friendly agrochemicals is imperative. While 3D printing is widespread, its potential in slow-release agrochemicals remains unexplored. This proof-of-concept study employed solvent casting and 3D printing to develop agar–urea structures. These structures, comprising 2.5% (w/w) agar, incorporated either 7% (w/w) or 13% (w/w) urea as nitrogen nutrients. Rheological, mechanical, and morphological properties and sorption capabilities were explored. Rheological analysis revealed a substantial impact of urea, enhancing material resistance to deformation. In mechanical tests, inclusion of urea showed no significant impact on compressive strength. SEM analysis confirmed the successful entrapment of urea within the agar matrix. The inclusion of urea resulted in a diminished water sorption capacity, attributed to the urea–water interactions disrupting the hydrogen bonding ability of agar. Agar–urea inks were employed in 3D printing utilizing the direct-ink writing technique, and the nitrogen release behavior was investigated. Results revealed nearly complete urea release in the positive control within 48 h. In contrast, agar–urea formulations with 7% (w/w) and 13% (w/w) achieved nitrogen release rates of 88.8% and 94.4%, respectively, suggesting potential for 3D-printed agar formulations to modify the immediate release behavior seen in conventional urea fertilizers. [ABSTRACT FROM AUTHOR]

Tertiary sulfonamide nitrogen-to-metal bonds of normal length are very rare. We recently discovered such a bond in one class of fac-[Re(CO)3(N(SO2R)(CH2Z)2)]n complexes (Z = 2-pyridyl) with N(SO5R)dpa ligands derived from di-(2-picolyl)amine (N(H)dpa). fac-[M(CO)3(N- (SO2R)(CH2Z)2)]n agents (M = 86/188Re, 99mTc) could find use as radiopharmaceutical bioconjugates when R is a targeting moiety. However, the planar, electron-withdrawing 2-pyridyl groups of IV(SO2R)dpa destabilize the ligand to base and create relatively rigid chelate rings, raising the possibility that the rare M--N(suifonamide) bond is an artifact of a restricted geometry. Also, the hydrophobic 2-pyridyl groups could cause undesirable accumulation in the liver, limiting future use in radiopharmaceuticals. Our goal is to identify a robust, hydrophilic, and flexible N(CH2Z)2 chelate framework. New C2-symrnetric ligands, N(SO2R)(CH2Z)2 with (Z = CH2NH2; R = Me, dmb, or tol), were prepared by treating N(H)dien(Boc)2, a protected diethylenetriamine (N(H)dien) derivative, with methanesulfonyl chloride (MeSO2Cl), 3,5-dimethylbenzenesulfonyl chloride (dmbSO2Cl), and 4-methylbenzenesulfonyI chloride (tolSO2Cl). Treatment of fac-[Re(CO)3(H2O)3]+ with these ligands, designated as N(SO2R)dien, afforded new fac-[Re(CO)3(N(SO2R)dien)]PF6 complexes. Comparing the fac-[Re- (CO)3(N(SO2Me)dien)]PF6 and fac-[Re(CO)3(N(SO2Me)dpa)]PF6 complexes, we find that the Re¹-N(sulfonamide) bonds are normal in length and statistically identical and that the methyl C NMR signal has an unusually upfield shift compared to that in the free ligand. We attribute this unusual upfield shift to the fact that the sulfonamide N undergoes an sp² -to-sp³ rehybridization upon coordination to Re¹ in both complexes. Thus, the sulfonamide N of N(SO2R)dien ligands is a good donor, even though the chelate rings are conformationally flexible. Addition of the strongly basic and potentially monodentate ligand, 4-dimethylaminopyridine, did not affect the fac-[Re(CO)3(N(SO2tol)dien)]PF6 complex, even after several weeks. This complex is also stable to heat in aqueous solution. These results indicate that N(SO2R)dien ligands form fac-[Re(CO)3(N(SO2R)dien)]PF6 complexes sufficiently robust to be utilized for radiopharmaceutical development. [ABSTRACT FROM AUTHOR]

We previously identified two new agents based on the [99mTcVO]3+ core with renal clearances in human volunteers 30% higher than that of the widely used clinical tracer 99mTc-MAG3 (MAG35- = penta-anion of mercaptoacetyltriglycine). However, renal agents with even higher clearances are needed. More recently, we changed our focus from the [99mTcVO]3+ core to the discovery of superior tracers based on the fac-[99mTcI(CO)3]+ core. Compared to 99mTc-MAG3, fac-[99mTcI(CO)3(NTA)]2- (NTA3- = trianion of nitrilotriacetic acid) holds great promise by virtue of its efficient renal clearance via tubular secretion and the absence of hepatobiliary elimination, even in patients with severely reduced renal function. We report here NMR, molecular (X-ray) structure, and solution data on fac-[ReI(CO)3(NTA)]2- with a -CH2CO2- dangling monoanionic chain and on two fac-[ReI(CO)3(L)]- analogues with either a -CH2CONH2 or a -CH2CH2OH dangling neutral chain. In these three fac-[ReI(CO)3(L)]n- complexes, the fac-[ReI(CO)3(N(CH2CO2)2)]- moiety is structurally similar and has similar electronic properties (as assessed by NMR data). In reported and ongoing studies, the two fac-[99mTcI(CO)3(L)]- analogues with these neutral dangling chains were found to have pharmacokinetic properties very similar to those of fac-[99mTcI(CO)3(NTA)]2-. Therefore, we reach the unexpected conclusion that in fac-[99mTcI(CO)3(L)]n- agents, renal clearance is affected much more than anticipated by features of the core plus the chelate rings (the [99mTcI(CO)3(N(CH2CO2)2)]- moiety) than by the presence of a negatively charged dangling carboxylate chain. [ABSTRACT FROM AUTHOR]